Answer:
Joey must get a score of 94 to have a average test score of <em>90</em>.
Step-by-step explanation:
Joey wants a average score of 90.
He already scored 91 and 85 on the previous two tests, and wants to know the score to get a 90 as an average.
Set the equation:
Average = (score of known tests + x)/(amount of tests in all).
Note that: x = score of the next test.
First, Plug in the corresponding numbers to the corresponding terms/variables:
90 = (91 + 85 + x)/(3)
Simplify. Isolate the variable, x. Note the equal sign, what you do to one side, you do to the other. Do the opposite of PEMDAS.
First, multiply 3 to both sides:
90(3) = (91 + 85 + x)/(3) * 3
270 = 91 + 85 + x
Isolate the variable x. Combine like terms:
270 = (91 + 85) + x
270 = 176 + x
Subtract 176 from both sides:
270 (-176) = 176 (-176) + x
x = 270 - 176
x = 94
Joey must get a score of 94 to have a average test score of <em>90</em>.
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