Question 9 - Figure it out - Page 102 to 105 - Chapter 4 Class 7 - Expressions using Letter-Numbers (Ganita Prakash)

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Question 9 (a) Subtract the expressions given below: (a) 9a – 6b + 14 from 6a + 9b – 18 Now, our expression is (6a + 9b – 18) – (9a – 6b + 14) = 6a + 9b – 18 – 9a + 6b – 14 = – 9a + 6a + 9b + 6b – 18 – 14 = –(9a – 6a) + (9b + 6b) – (18 + 14) = – 3a + 15b – 32 Question 9 (b) Subtract the expressions given below: (b) –15x + 13 – 9y from 7y – 10 + 3x Now, our expression is (7y – 10 + 3x) – (–15x + 13 – 9y) = 7y – 10 + 3x + 15x – 13 + 9y = 7y + 9y + 3x + 15x – 13 – 10 = (7y + 9y) + (3x + 15x) – (13 + 10) = 16y + 18x – 23 Question 9 (c) Subtract the expressions given below: (c) 17g + 9 – 7h from 11 – 10g + 3h Now, our expression is (11 – 10g + 3h) – (17g + 9 – 7h) = 11 – 10g + 3h – 17g – 9 + 7h = – 17g – 10g + 3h + 7h + 11 – 9 = –(17g + 10g) + (3h + 7h) + (11 – 9) = –27g + 10h + 2 Question 9 (d) Subtract the expressions given below: (d) 9a – 6b + 14 from 6a – (9b + 18) Now, our expression is (6a – (9b + 18)) – (9a – 6b + 14) = 6a – (9b + 18) – 9a + 6b – 14 = 6a – 9b – 18 – 9a + 6b – 14 = – 9a + 6a – 9b + 6b – 18 – 14 = –(9a – 6a) – (9b – 6b) – (18 + 14) = –3a – 3b – 32 Question 9 (e) Subtract the expressions given below: (e) 10x + 2 + 10y from –3y + 8 – 3x Now, our expression is (–3y + 8 – 3x) – (10x + 2 + 10y) = –3y + 8 – 3x – 10x – 2 – 10y = – 10y – 3y – 3x – 10x + 8 – 2 = – (10y + 3y) – (3x + 10x) + (8 – 2) = – 13y – 13x + 6 Question 9 (f) Subtract the expressions given below: (f) 8g + 4h – 10 from 7h – 8g + 20Now, our expression is (7h – 8g + 20) – (8g + 4h – 10) = 7h – 8g + 20 – 8g – 4h + 10 = 7h – 4h – 8g – 8g + 20 + 10 = (7h – 4h) – (8g + 8g) + (20 + 10) = 3h – 16g + 30