In answer choice A the fractions are 3/6 and 4/6. In the original equation in fractions are 1/2 and 2/3. The equivalent fraction to 1/2 is 3/6 because 1x3=3 and 2x3=6, therefore 3/6 is equivalent. The equivalent fraction to 2/3 is 4/6 because 2x2=4 and 3x3=6, therefore 4/6 is equivalent.
In answer choice D the fractions are 9/18 and 12/18. In the original equation in fractions are 1/2 and 2/3. The equivalent fraction to 1/2 is 9/18 because 1x9=9 and 2x9=18, therefore 9/18 is equivalent. The equivalent fraction to 2/3 is 12/18 because 2x6=12 and 3x6=18, therefore 12/18 is equivalent.
11/21 / 22/7 is the same as or = to 11/21 * 7/22 which = 77/462 and then divide both the numerator and denominator by 77 and you get 1/6. (In other words simplify 77/462). Hope this helped :)
