So I'll walk through the first 2. Then please try the other ones and let me know if you run into more problems.
5m-6
If m is equal to 7, then replace m with 7.
5(7)-6
5x7=35 so the expression is now 35-6. Solve.
35-6=29
So that was the first one.
4m+t
We just do what we do with the first problem.
4(7)+(2)
4x7=28 so the expression is 28+2.
28+2=28
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hope it helps
p.s. When there is subtraction, add. When there is division, multiply to cancel that out. When there is multiplication, divide to cancel. etc.