Convert the mixed number 2 1/4 into an improper fraction: 9/4.
Then multiply this 9/4 by 3: 27/4, or 6 3/4.
(35 + 47 + 42 + x) / 4 = 50
(124 + x) / 4 = 50....multiply both sides by 4, cancelling the 4 on the left side.
124 + x = 50 * 4
124 + x = 200
x = 200 - 124
x = 76 <===