Answer
d=81
Work Step by Step
In order to solve this algebraic expression, we must isolate the variable. A variable is the letter in the problem (for instance, in the equation 2x=10, x is the variable).
In the expression 36=4/9 d, d is being multiplied by a fraction, which we must cancel out. In order to cancel out a fraction being multiplied by a variable, we multiply both sides of the equation by the reciprocal of the fraction, which is the fraction flipped upside down. (For instance, the reciprocal of ⅖ is 5/2).
Thus, we multiply both sides of the equation by 9/4 to obtain that d=81. When we plug d=81 into the initial equation, we get that $36=36$, so the solution is correct.