Practise that problems till you can understand it first or second time it will be wrong but third time it will be right solve it like a puzzle or maze.... plz mark it as a brainest answer
understand the questions not do rattafication then the maths will be difficult for you
i had try that's why
According to me , 
step 1understand the question first
step 2: write all the given information
step 3:  understand what to find 
step 4 : write the formula wherever necessary
step 5 finally try to solve the question

the girl went to the shop and she buy 4 pens of Rs.3 each, 2 notebooks of Rs 10 each. and she paid Rs. 50 to the shop keeper then how much she will get her balance.

  1 pen = Rs.3
  4 pens = Rs 4x3 = 12
1 notebook = Rs.10
2 notebooks = 10 x 2 = 20
so she have to pay = 12 + 20 = 32 Rs.
but she paid Rs. 50 
so, she has to get balance = Rs. 50 - 32 = Rs.18
(I gave simple sum to understand)