Solve the problem in the attached image

If 20% of a number is 35, what is 50% of that number?

How do i start to solve? would appreciate a walk-thru! a bird sitting 16ft above the ground in an apple tree dislodges an apple. after how many seconds does the apple land on the ground? (assuming that no branches will interfere with it's fall)

Find the value of x. round the length to the nearest tenth