Answer:
t1 = $25m
t2 = $(10m + 100)
Explanation:
Here we want to write equations
Kiera chose plan 1
$25 monthly and no joining fee
So the amount after m months will be 25 * m
t1 = $25m
Trina chose plan 2
$10 a month and $100 joining fee
after m months , total payment will be
10(m) + 100 = $(10m + 100)
Thus t1 = $25m and t2 = $(10m + 100)