This document contains a series of math problems involving addition, subtraction, multiplication and order of operations. The problems are arranged in groups and provide the step-by-step work to solve basic arithmetic expressions.

1. CALCULO MENTAL
3 X 3 + 8 17
2 X 8 – 9 7
4 X 5 + 6 – 4 22
5 X 3 – 7 + 9 17

2. 4 + 10 – 7 + 5 12
5 + 12 – 4 + 6 19
3 X 7 – 4 + 6 23
4 X 8 – 3 + 10 39

3. 8 + 7 – 4 + 6 17
9 + 8 – 3 +10 24
2 X 9 – 5 + 8 21
3 X 6 – 4 + 9 23

4. 12- 5 + 7 -3 11
13 – 6 X 3 +5 26
4 X 4 – 9 + 5 12
5 X 5 – 4 +7 28