j/6 = 9/10 is the proportion that we are trying to solve. Let's use cross products, or multiplying the numerator of one fraction by the denominator of the other fraction, and setting these two numbers equal to one another in an equation.
9 (6) = 10 (j)
When we combine like terms (multiply), we get
54=10j
We need to divide both sides by 10, to get the variable alone.
j = 5.4
