a)

N + 7 = 18 subtract 7 from both sides

N = 11

b)

N - 6 = 24 add 6 to both sides

N = 30

c)

5N = 45 divide both sides by 5

N = 9

d)

N/6 = 7 multiply both sides by 6

N = 42

e)

4N + 3 = 19 subtract 3 from both sides

4N = 16 divide both sides by 4

N = 4