Question 775210
{{{x}}}= score on the next test
The average of all 5 scores would be
{{{(68+78+90+91+x)/5=(327+x)/5}}}

I would think that a calculated average of 84.5 or 84.6 would be reported as 85, but that would complicate the problem. So I expect that the average needs to be what your science teacher would call 85.0 or larger, and your math teacher would call just 85 or larger. Then the inequality would be
{{{(327+x)/5>=85}}} --> {{{327+x>=85*5}}} --> {{{327+x>=425}}} --> {{{x>=425-327}}} --> {{{x>=98}}}