Question

Three friends went to a bookshop. the first bought 3biros and 5pencils for $30.00 and second bought 2biros and 5pencils for$27.00 and the third bought a biro and apencil only.How much did he pay.?​

Answer 1

X = Biro

Y = Pencil

3X + 5y = 30

2X + 5Y = 27

X + Y = ?

Analysing these two, you can see that one biro costs $3

3X + 5Y = 30

2X + 5Y = 27

So, we are allowed to do it:

5Y = 21

Y = 21 / 5

Y = 4,2

each pencil costs $ 4,2

The third one pays $ 7,2