It seems confusing, but it's just breaking down the steps for you. It's done the same as any other word problem.
a. The unknown is how many minutes she used beyond the plan. So, we'll use "m" for the variable, to represent minutes.
b. 73.40 = 65 + 0.10m
The 73.40 is the total, which is why it's by itself. 65 represents the price per month for the plan, and 0.10m is the price per extra minute multiplied by the unknown amount of minutes used.
c. 73.40 = 65 + 0.10m
8.40 = 0.10m
84 = m
d. The number of minutes that Allegra went over the time that the plan allows is found by solving the equation we just wrote and solved. $0.10 is paid for every minute past the plan's allowance, meaning that "m" in the equation, when solved, shows us exactly how many minutes over Allegra went.
In dividing two equation with variables and exponent, First you must align or rearrange the equation and group them base on their variables but don't forget the sign of each variables. Second, proceed in dividing its quantity and then subtract its exponent to the other variables having the same. So by calculating it, the answer would be X or X^1