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 = x 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 
Let, Number of toys with Kabir 
Let, Number of toys with Kabir 
Let, Weight of Sumit’s grand father = w 
Weight of Sumit = w/3 