13 = 2f + 5
i don't know how to solve this

Simplifying 13 = 2f + 5
 Reorder the terms: 13 = 5 + 2f
 Solving 13 = 5 + 2f
 Solving for variable 'f'.
 Move all terms containing f to the left, all other terms to the right.
 Add '-2f' to each side of the equation. 13 + -2f = 5 + 2f + -2f
 Combine like terms: 2f + -2f = 0 13 + -2f = 5 + 0 13 + -2f = 5
 Add '-13' to each side of the equation. 13 + -13 + -2f = 5 + -13
 Combine like terms: 13 + -13 = 0 0 + -2f = 5 + -13 -2f = 5 + -13
 Combine like terms: 5 + -13 = -8 -2f = -8
  Divide each side by '-2'. f = 4
 Simplifying f = 4

SO, f = 4

13 = 2 × 4 + 5

Hope I helped:P