Question

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Answer 1

use substitution method....
It's a method when we replace the value of one variable from the other equation....

Google it, for better explanation :)

Answer 2

^^

Substitute n - 4 for m in the 1st equation:

m + 5n = 20

n - 4 + 5n = 20

Simplify n + 5n:

6n - 4 = 20

Add 4 to both sides, what's 20 + 4?

Answer 3

In the first equation, replace m with n-4. Then you can use the first equation to solve for n. Use the value of n to solve for m, in the second equation.

Answer 4

Yep, that gives us:

6n = 24

Now divide 24 / 6, what do you get?