The least common denominator is the Least Common Multiple (LCM) of the divisors 3 and 4. Since these numbers have no common factors, their LCM is
... 3·4 = 12
The least common denominator of your fractions is 12.
... 1/3 = (1/3)·(4/4) = 4/12
... 3/4 = (3/4)·(3/3) = 9/12

; where a = 1, b = -4 and c = -38
So, since the student makes $30 each week, we can disregard the number of hours.
So, we can model this situation by the following equation
9.5h+30
So, if he works 10.25 hrs (15 minutes = .25 of 1 hr) we just plug that number in

Since it's money we round to the nearest cent
So he will make $127.28 Next week
So:
(x-4)(x+2) / (x-4)(x+4)
We cancel out the x - 4:
(x+2)/(x+4)
Restrictions: x ≠ 4, x ≠ -4