3-(s+4)
less than- subtract
sum- addition
since it said 3 less than the sum of a number and 4 that means you would have to add s and 4
X=40 degrees because it s on the circle. arc AD+arc DC=180 arc DC is 100 so AD is 80. That means x must be 40.
I think this is the answer to your question And also the solution