n=30-8m

in eq.2

m-7(30-8m)=18

m-210+56m=18

57m=228

m=228/57=4

thus,n=30-32=-2

m = 18 + 7n

then substitute (18 + 7n) in place of the m in the first equation and solve to get a numerical value of n. Once you know n, come back to the equation m = 18 + 7n to get the numerical value of m.

m-7n=18

first, try to get one of the variables alone. it doesnt matter which equation you start with.

n=30-8m

then, plug this new equation into the second one.

the second equation now becomes

m-7(30-8m)=18

m-210+56m=18

m+56m=18+210

57m=228

228/57=4

m=4

now that you have m, plug that back into the original equation

8(4)+n=30

36+n=30

n=30-36

n= -6

so, your answer is m=4, n= -6