Question 198128
Let {{{a}}}= the cost of 1 apple
Let {{{g}}}= the cost of 1 grape
given:
(1) {{{3a + 5g = 170}}} (in cents)
(2) {{{5a + 3g = 246}}} (in cents)
Multiply both sides of (1) by {{{5}}}
Multiply both sides of (2) by {{{3}}}
Subtract (2) from (1)
(1) {{{15a + 25g = 850}}} 
(2) {{{-15a - 9g = -738}}}
------------------------
{{{16g = 112}}}
{{{g = 7}}}
The cost of 1 grape is 7 cents
check answer:
{{{3a + 5*7 = 170}}}
{{{3a + 35 = 170}}}
{{{3a = 170 - 35}}}
{{{3a = 135}}}
{{{a = 45}}}
and
{{{5a + 3g = 246}}}
{{{5*45 + 3*7 = 246}}}
{{{225 + 21 = 246}}}
{{{246 = 246}}}
OK