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# Evaluating an expression with one variable

Learn how to evaluate an expression with variables using a technique called substitution (or "plugging in"). Created by Sal Khan and Monterey Institute for Technology and Education.

Video transcript

A local hospital is holding a raffle. The individual cost of participating in the raffle is given by the following expression 5t + 3 or 5 * t + 3, where t represents the number of tickets one purchases. evaluate the expression when t = 1, t = 8 & t = 10 Lets first take the situation when t = 1, so the expression becomes 5 * 1 + 3 and we know from order of operations, we do the multiplication before we do the addition. so ( 5 * 1) + 3 = 5 + 3 = 8. Now we do it when t = 8, this expression becomes (5 * 8) + 3 = 40 + 3 = 43 so we have the last situation when t = 10 so we have ( 5 * 10) + 3 = 50 + 3 = 53 and we are done