Question

Un muchacho compra el mismo numero de lapices que de lapiceros por 90 soles.Cada laliz le cuesta 3 soles y cada lapicero 7 soles. ¿Cuantos lapices y lapiceros ha comprado?

Answer 1

pencils amount = 9 pens amount= 9

Explanation:

We start this problem forming two linear equations system.

3*X+7*Y=90

Where X is the amount of pencils and Y is the amount of pens

The second equation is given by the statement, the amount of pencils is equal to the amount of pens, so the second equation is:

X=Y

Merging both equations we have:

3*X+7*X=90

Solving for X we have:

10*X=90

X=9

X=Y=9