To solve a proportion, you always cross multiply and then solve for the variable by isolating the variable.
1) First, you cross multiply to get 14x=20*56 or 14x=1120. Then, you divide both sides by 14 to get x=80 (C).
2) First, you cross multiply to get 16d=6*12 or 16d=72. Then, you divide both sides by 16 to get d=4.5 (B).
3) First, you cross multiply to get 35y=15*224 or 35y=3360. Then, you divide both sides by 35 to get y=96 (C).