Let x be the cost of Jane's meal as stated in the question.
Greg's dinner cost $24. Total cost of dinner = (x + 24)
Tip 15% of dinner cost. Tip was $9.
15% of (x + 24) = 9
(15/100)(x + 24) = 9
0.15(x + 24) = 9. That's the equation. Question answered.
But let's just go ahead and find x for the fun of it.
0.15*(x + 24) = 9.
(x + 24) = 9/0.15
(x + 24) = 60
x = 60 - 24
x = 36
x, which, Jane's dinner cost = $36.
