How do you do 5d-6 equals 9 solved by two step equations?

5d - 6 = 9

1sr step.

Add '6' to both sides

Hence

5d = 15

2nd step

Divide both sides by '5'.

d = 3 (The solution).

NB For addition(+), subtraction(-), Multiplication(x) and division(/), whatever you do to one side of the eq'n, you MUST do to the other side, otherwise it is no longer 'equal(=).