Final answer:
To find the missing term in the equivalent ratio, cross multiply the given ratio and solve for the missing term.
Step-by-step explanation:
In order to find the missing term in the equivalent ratio, we can use the property of cross multiplication. Cross multiplying the given ratio, we have: 81 * x = 18 * 36. Solving for x, we get x = (18 * 36) / 81 = 8.