Let’s learn how to convert a situation into an expression.
First
we find variable in our situation
and then make an expression.
Situation 
Variable 
Expression 
Sarita has 10 more

Let Marbles with Ameena = x 
Marbles with Sarita = x + 10 
Balu is 3 years

Let Raju’s Age = x years 
Balu’s age = (x − 3) years 
Bikash is twice

Let, Raju’s age = x years 
Bikash’s age = 2 × 𝑥 = 2x years 
Raju’s father’s age is 2 years more than 3 times Raju’s age. 
Let Raju’s Age = x years 
Raju’s father's age = (3x + 2) years 
How old will Susan

Let, Susan’s Age = y years 
Susan’s age
= (y + 5) years 
How old was Susan

Let, Susan’s Age = y years 
Susan’s age
= (y − 4) years 
Price of wheat per kg is rupees 5 less 
Let, Price of rice per kg = p Rupees 
Price of wheat per kg = (p − 5) rupees 
Price of oil per litre

Let, Price of rice per kg = p Rupees 
Price of oil per litre = 5p rupees 
The speed of a bus is

Let, Speed of truck = y km/hr 
Speed of bus = (y + 10) km/hr 
Ali has twice as much apps as Nandan do. 
Let,
Number of apps

No. of apps with Ali = 2x 
Rajshri has got 3 more certificates than Kamal. 
Let,
No: of certificates

No: of certificates that Rajshri has = x + 3 
Anthony has 10 toys less than Kabir 
Let, Number of toys with Kabir = x 
Let, Number of toys Anthony have = x  10 
Sumit's weight is onethird of his grandfather's weight 
Let, Weight of Sumit’s grand father = w 
Weight of Sumit = w/3 