6.
x = x/a + b
x - b = x/a
ax - ab = x
ax - x = ab
x(a - 1) = ab
x = ab/(a - 1)
7. x/3 + x/a = 1
x + 3x/a = 3
ax + 3x = 3a
x(a + 3) = 3a
x = 3a/(a + 3)
8. x/a + bx = c/a
x(1/a + b) = c/a
x = c/a(1/a + b)
x = c/(ab + 1)
9. x/a - 2x = c
x(1/a - 2) = c
x = c/(1/a - 2)
x = ac/(1 - 2a)
10. x/a = b + 3x
x/a - 3x = b
x(1/a - 3) = b
x = b/(1/a - 3)
x = ab/(1 - 3a)