Question 18 - Figure it out - Page 185 to 189 - Chapter 7 Class 7 - Finding the Unknown (Ganita Prakash II)

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Question 18 Solve these equations: (a) 5(r + 2) = 10Solving 5(r + 2) = 10 5 × r + 5 × 2 = 10 5r + 10 = 10 Putting 10 on right side, so it becomes –10 5r = 10 – 10 5r = 0 Putting 5 on right side, so it becomes division r = 0/5 r = 0 Question 18 Solve these equations: (b) – 3(u + 2) = 2(u – 1)Solving – 3(u + 2) = 2(u – 1) Opening bracket –3 × u + (–3) × 2 = 2 × u – 2 × 1 –3u – 6 = 2u – 2 Putting –6 on right side, so it becomes +6 –3u = 2u – 2 + 6 –3u = 2u + 6 – 2 –3u = 2u + 4 Putting 2u on left side, so it becomes –2u –3u – 2u = 4 –u × (3 + 2) = 4 –u × 5 = 4 u × –5 = 4 Putting –5 on right side, so it becomes division Note: –5 doen’t become +5 on right side, since it is dividing u = 4/(−5) u = (−𝟒)/𝟓 Question 18 Solve these equations: (c) 2(7 – 2n) = – 6Solving 2(7 – 2n) = –6 Opening bracket 2 × 7 – 2 × 2n = –6 14 – 4n = –6 Putting 14 on right side, so it becomes –14 –4n = –6 – 14 –4n = – (6 + 14) –4n = –20 Putting –4 on right side, so it becomes division Note: –4 doen’t become +4 on right side, since it is dividing n = (−𝟐𝟎)/(−𝟒) n = 20/4 n = 5 Question 18 Solve these equations: (d) 2(x – 4) = – 16Solving 2(x – 4) = –16 Opening bracket 2 × x – 2 × 4 = –16 2x – 8 = – 16 Putting –8 on right side, so it becomes +8 2x = –16 + 8 2x = – (16 – 8) 2x = –8 Putting 2 on right side, so it becomes division x = (−𝟖)/𝟐 x = –4Question 18 Solve these equations: (e) 6(x – 1) = 2(x – 1) – 4Solving 6(x – 1) = 2(x – 1) – 4 Opening bracket 6 × x – 6 × 1 = 2 × x – 2 × 1 – 4 6x – 6 = 2x – 2 – 4 6x – 6 = 2x – (2 + 4) 6x – 6 = 2x – 6 Putting –6 on right side, so it becomes +6 6x = 2x – 6 + 6 6x = 2x + 0 6x = 2x Putting 2x on left side, so it becomes –2x 6x – 2x = 0 4x = 0 Putting 4 on right side, so it becomes division x = 0/4 x = 0 Question 18 Solve these equations: (f) 3 – 7s = 7 – 3sSolving 3 – 7s = 7 – 3s Putting +3 on right side, so it becomes –3 –7s = 7 – 3s – 3 –7s = –3s + 7 – 3 –7s = –3s + 4 Putting –3s on left side, so it becomes +3s –7s + 3s = 4 –(7s – 3s) = 4 –4s = 4 Putting –4 on right side, so it becomes division Note: –4 doen’t become +4 on right side, since it is dividing s = 𝟒/(−𝟒) s = (−4)/4 s = 1 Question 18 Solve these equations: (g) 2x + 1 = 6 – (2x – 3)Solving 2x + 1 = 6 – (2x – 3) Opening bracket 2x + 1 = 6 – 2x + 3 2x + 1 = –2x + 6 + 3 2x + 1 = –2x + 9 Putting 1 on right side, so it becomes –1 2x = –2x + 9 – 1 2x = –2x + 8 Putting –2x on left side, so it becomes +2x 2x + 2x = 8 4x = 8 Putting 4 on right side, so it becomes division x = 8/4 x = 2 Question 18 Solve these equations: (h) 10 – 5x = 3(x – 4) – 2(x – 7)Solving 10 – 5x = 3(x – 4) – 2(x – 7) Opening bracket 10 – 5x = 3x – 3 × 4 – 2x + 2 × 7 10 – 5x = 3x – 12 – 2x + 14 10 – 5x = (3x – 2x) + (14 – 12) 10 – 5x = x + 2 Putting 10 on right side, so it becomes –10 –5x = x + 2 – 10 –5x = x – 10 + 2 –5x = x – (10 – 2) –5x = x – 8 Putting x on left side, so it becomes –x –5x – x = –8 –x × (5 + 1) = –8 –x × 6 = –8 –6x = –8 Putting –6 on right side, so it becomes division Note: –6 doen’t become +6 on right side, since it is dividing x = (−𝟖)/(−𝟔) x = 8/6 x = 𝟒/𝟑