1. (7a + 4b) + (8a - 6b) =...... 2. (15i + 14b + 13k) + (-30i - 45j + 51k)=..... 3. (42n + 35m + 7) - (50m - 20n + 9)=..... 4. (5x + 3) = x-1 5. 6x + 4 = x -y

1. (7a + 4b) + (8a - 6b)
= 7a + 8a + 4b - 6b
= 15a - 2b.

2. (15i + 14b + 13k) + (-30i - 45j + 51k)
= 15i + (-30i) + 14b + 13k + 51k - 45j
= -15i + 14b + 64k - 45j.

3.(42n + 35m + 7) - (50m - 20n + 9)
= 42n - 20n + 35m - 50m + 7 + 9
= 22n - 15m + 16.

4.(5x + 3) = x-1
5x-x = -1 - 3
4x = -4
x = - 4 ÷ 4
x = -1.