(Q1)t=0.15b what is the tip for a bill for 18.49 (Q2)c=0.55+0.15m 7 minutes, c is for cost, m is for min.?

Question

t is for tip and b is for bill on the first question.

On the second question c is for cost and m is for minutes

Answer 1

1.) t = 0.15b (i.e. a 15% tip). For a bill of 18.49, the tip is:
t = 0.15 * 18.49
t = $2.77

2.) c=0.55+0.15m. For 7 minutes, c =
c = .55 + .15 * 7
c = .55 + 1.05
c = 1.60

Essentially, since you're given the value for one of the variables, just replace the variable with the value given, then do the math as normal.