Question

A shop sells one pound bags of peanuts for $2 and three pound bags of peanuts for $5. If 9 bags are purchased for a total of $36 how many one pound bags were purchases

Answer 1

x=number of 1lb bags
y=number of 3lb bags


2x+5y=36
and
x+y=9

mulitply 2nd equation by -2 and add to first equation

2x+5y=36
-2x-2y=-18 +
0x+3y=18

3y=18
divide both sides by 3
y=6
sub back

x+y=9
x+6=9
x=3


there were 3 one pound bags bought