Tina scored 94, 68, and 88 on her first 3 algebra 1 test. her next test is her final which counts double. write and solve an equation that tina could use to determine the minimum grade she must score on her final to have a mean score of 80.

To find the minimum score, you will consider that the mean of 80 must spread out between all possible scores.  

Because the last exam counts double, you will consider 5 scores.

5 x 80 = 400 total points are what Tina needs.

400 - (94 + 68 + 88) = 150.

She must earn half of 150 points on her exam to earn an 80% overall grade.

A 75 is what Tina will need.