Robs lunch cost is unknown = x
and we know carla's cost 15 = 15
x + 15 = total lunch cost
now me know 20% is 6
so 20% of total lunch cost is 6
or
(x+15)(.02) which is 20% of lunch and this is 6
or
(x+15)(.02) = 6 this is the equation to find x
this is the answer, but for kicks lets solve it to to find the cost
.2x + 3 = 6
- 3 -3
.2x = 3
/.2 /.2
x = 15
Robs lunch cost $15 too
