Answer:
39.1
Step-by-step explanation:
((31.7+ 42.8+26.4+x))/(4)=35
There are four things that you add, so you have to divide by 4. Your end result is 35, so set your equation equal to 35.
4 times 35 is 140.
The stuff remaining is 100.9 + x = 140
140-100.9 is 39.1
