Finals Grade to Pass

Hi, I'm hoping you can help me. Please provide evidence on how you got the answer because I'm stress. I have a really hard time in school due to my mental illness. Please don't judge. I really hope you can help

Each of my finals are worth 10%

I need to know what grade I have to get in order to get a 70% which is passing

Class 1: Grade is a 77%
Class 2: Grade is a 71%
Class 3: Grade is a 75%

Thank you SO much.

77(0.9) + X(0.1) = 70 need 7 points on the final
71(0.9) + X(0.1) = 70 need 61 points on the final
75(0.9) + X(0.1) = 70 need 25 points on the final

This considered Class 4: ?

You need at least a 57% to pass.

(77+71+75+x)/4 = 70
(223+x)/4 = 70
223+x = 280
x= 57


Oh... I understood this question incorrectly. The below answer is correct.