Question

Amy purchased 17 pencils and 18 pens for a fund-raiser at school and spent $61.50. Jocelyn purchased 10 pencils and 21 pens and spent $57. How much does each pencil cost?

Answer 1

x = pencils, y = pens

17x + 18y = 61.50....multiply by 21
10x + 21y = 57 ....multiply by -18
------------------------
357x + 378y = 1291.5 (result of multiplying by 21)
-180x - 378y = - 1026 (result of multiplying by -18)
-----------------------add
177x = 265.5
x = 265.5 / 177
x = 1.50 <== cost for a pencil
pens(y) cost 2.00