Question

Jasmine has 24 erasers and Muthu has 20 erasers.How many erasers must Muthu give to Jasmine so that she will have thrice the number of erasers that Muthu has?

Answer 1

Let's mark number of Jasmine's erasers by J and the number of Muthu's erasers by M.
N - the unknown number of erasers.
J + N = 3(M - N)
J + N = 3M - 3N
4N = 3M - J
N = (3M - J)/4 = (3*20 - 24)/4 = 9.
So, Muthu must give 9 erasers to Jasmine.