Question 151540
Let x=score on 4th test



Remember, to find the average of 4 numbers, simply add the 4 numbers up and divide that sum by 4 (the number of numbers)



So the average of the 4 tests is:


{{{A=(97+82+86+x)/4}}}



In order to "make at least a 90 average", we need an average that is greater than or equal to 90. So this means that 


{{{A>=90}}}



{{{(97+82+86+x)/4>=90}}} Plug in {{{A=(97+82+86+x)/4}}}. In other words, replace "A" with {{{(97+82+86+x)/4}}}



{{{97+82+86+x>=360}}} Multiply both sides by 4.



{{{265+x>=360}}} Combine like terms.



{{{x>=360-265}}} Subtract {{{265}}} from both sides.



{{{x>=95}}} Combine like terms on the right side.



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Answer:


So the answer is {{{x>=95}}} which means that Jesse needs a 95 or higher on the 4th test to average a 90 or better.