Question 968381
I assume this is a real life problem.
If so, at this point, I should not waste your time with lengthy explanations.
{{{x}}}= grade on the final exam
{{{final}}}{{{grade=0.7*63.1+0.3x}}}
{{{final}}}{{{grade=44.17+0.3x}}}
For a 70:
{{{44.17+0.3x=70}}}
{{{0.3x=70-44.17}}}
{{{0.3x=25.83}}}
{{{x=25.83/0.3}}}
{{{x=86.1}}}
For an 80:
{{{44.17+0.3x=80}}}
{{{0.3x=80-44.17}}}
{{{0.3x=35.83}}}
{{{x=35.83/0.3}}}
{{{x=119.4}}}
So, there is no chance for an 80.
With a 100 on the final:
{{{final}}}{{{grade=44.17+0.3*100}}}
{{{final}}}{{{grade=44.17+30}}}
{{{final}}}{{{grade=74.17}}}