Determine the equation of the line using the given slope and point by, y - y1 = m(x - x1) Substitute the values, y - 6 = 5(x - 5) Simplifying the equation, y = 5x - 19 Substituting the given value of x given, y = 5(21) - 19 = 86 Therefore, the answer is 86.
(think: what times 4 is 12? 3! so we need to muliply both sides of the equal sign by 3, so we can turn the 4 into a 12. Remember, what you do to on side, you must do to the other. )