I hope you don't find the solution too messy. If there is anything you don't get. Let me know and I will explain it:
1 + 1x
OR
1 + x
They mean the same thing! Hope this helps!
It is C. r=6
3 * 6 = 18 + 2 =20
1. substitute:
4+(7-5)
2. simplify:
4+2
3. evaluate:
6
the answer is 6.