Here's the correct matching of equations with the steps to solve them:
5x = 0.4 : Multiply each side by 5 (Choice 1)
x/5 = 8 : Multiply each side by 5 (Choice 1)
3 = -x/5 : Multiply each side by -5 (Choice 2)
7 = -5x : Multiply each side by -1/5 (Choice 4)