Answer:
x ≥ 64
Explanation:
We want to find the average
Let x be the 5th grade
We want it to be no less than 80
Add up the scores and divide by 5
( 80+ 72+ 96+ 88+x)/5 ≥ 80
Combine like terms
( 336+x) /5 ≥ 80
Multiply each side by 5
336+x ≥ 400
Subtract 336 from each side
x ≥ 400-336
x ≥ 64