Okay so I think I got it right, I just need someone to check over it. Here's what I learned for this equation
M=y2-y1/x2-x1
Then when you plug it in its.
M=10-8/12-4
Then when I did those equations I got 2/6
But then It needs to be simplified
2/6=1/3
Did I get it right?

Onnie is considering doing some long term investing with money that she inherited. she would like to have $50,000 at the end of 30 years. approximately how much money would lonnie need to put into an account earning 6% interest compounded annually in order to meet her goal?