When you are told to estimate, you should be able to do the problem in your head.
8 7/12 is close to 8 1/2
4 7/8 is very nearly 5
4/10 is very nearly 1/2
8 1/2 - 5 - 1/2 First of all you can take the 1/2 away from 8 1/2
8 1/2 - 1/2 = 8
Now take away the 5
8 - 5 = 3
So the answer is very nearly
3 <<<<< answer.
Just for fun, I'll get the exact answer. Don't hand this one in. It is 3 37/120
You learn to estimate because you are trying to guess whether or not you've entered everything correctly into your calculator. When writing a test, this is a very handy skill to have developed.
Here's the graph of your equation, instructions on how to plot is in the image. if there's a second line equation, you could use the method shown to plot that too, and the x and y values of the intersection point would be your answer.
you could also use algebra to simultaneously solve the two equations to obtain x and y as well, feel free to ask!
hope that helps :) sorry it's not a definite answer