Answers with step-by-step explanation:
1. (7x + x) + 7x
= 7x + 7x + x
= 14x + x
= 15x
2. 5 * (4 * x)
= 5*4x
= 20x
3. 15y + (x + 9y)
= 15y + 9y + x
= 24y + x
4. (6x + 21) + 14
= 6x + 21 + 14
= 6x + 35
5. 3x + 2 + 11x
= 11x+ 3x + 2
= 14x + 2
6. (x + 13y) + 8y
= 13y + 8y + x
= 21y + x
7. (12y + 2x) + 4y
= 12y + 4y + 2x
= 16y + 2x
8. 8 (x4)
= 32x
9. 3 (5x)
= 15x
10. 3x + (7x + 10)
= 3x + 7x + 10
= 21x + 10
11. 5x + (2 + x)
= 6x + 2
12. 4 * x * 10
= 4 * 10 *x
= 40x
13. (x * 12) * 3
= 36x
14. 14x + 9y + 6x
= 20x + 9y
15. 5x + (24 + 14x)
= 19x + 24