APR=18%
Monthly interest = 18/12=1.5%
If Caitlyn paid before due date,
amount liable for interest charges = 375-250 = $125
Interest charge for the month
=$125*1.5%
=$1.88
If a single expression is required, then
interest = (375-250)*0.018/12 = $1.88 to the nearest cent.
To solve for r, you would start by subtracting p from both sides.
2m - p = -q/r
Multiply everything by r.
2mr - pr = -q
Factor r out of the left side of the equation.
r(2m - p) = -q
Divide both sides by (2m - p).
r = 
.
60, 60 and 60 degrees
There are two criteria: the angles have to all be equal and they have to add up to 180 degrees. This answer satisfies both criteria.
