1. Solve proportion 12/15 = 18/b

2. Solve equations

A. - x + 4 = x + 6

B. 5n + 7 = 7 (n+1) - 2n

C. - 4 (p+2) + 8 = 2 (p-1) - 7p + 15

3. Solve a/b x - c = 0 for x

We solve the as follows:

1. Solve proportion 12/15 = 18/b

(12/15 = 18/b) b

(12b/15 = 18) 15/12

b = 18 (15/12)

b = 45/2

2. Solve equations

A. - x + 4 = x + 6

-x + 4 - x = x + 6 - x

-2x + 4 - 4 = 6 - 4

-2x = 2

x = - 1

B. 5n + 7 = 7 (n+1) - 2n

5n + 7 = 7n + 7 - 2n

5n - 7n + 2n = 7 - 7

0 = 0

C. - 4 (p+2) + 8 = 2 (p-1) - 7p + 15

-4p - 8 + 8 = 2p - 2 - 7p + 15

-4p + 7p - 2p = - 2 + 15 + 8 - 8

p = 13

3. Solve a/b x - c = 0 for x

a/b x - c = 0

(a/b x = c) b/a

x = bc / a