28x+4 14x+7
45x-30 / 30x-20
the way you do these is the same way you divide by fractions:
(a/b) ÷ (c/d) = (a/b)(d/c) = (ad)/(bc)
in this case, a = 28x + 4, b = 45x - 30, c = 14x + 7, and d = 30x - 20. so we get:
$\displaystyle \frac{\frac{28x+4}{45x-30}}{\frac{14x+7}{30x-20}} = \frac{(28x+4)(30x-20)}{(45x-30)(14x+7)}$
$\displaystyle = \frac{(4(7x+1))(10(3x-2))}{(15(3x-2))(7(2x+1))} = \frac{40(7x+1)}{105(2x+1)}$
$\displaystyle = \frac{8(7x+1)}{21(2x+1)} = \frac{56x+8}{42x+21}$