x + 4 = 15
- 4 -4
x = 11
You would subtract 4 because you need to isolate the x to get the value of x. You would subtract it to both sides because whatever you do on one side, you have to do it to the other side.
Answer:
Distribute the 5 to get 10a-15=20+a and solve
The answer is 23 because you would substitute in the 4 for the X and multiply 5 times 4 = 20 then add 20 plus 3 and you get 23
