What is the value of m? 12+(7+m)=30 11 19 25 35 49

We can do anything to an equation as long as we do it to both sides
remember the associative property of addition

a+(b+c)=(a+b)+c
so
12+(7+m)=(12+7)+m=19+m

19+m=30
minus 19 both sides
19-19+m=30-19
0+m=11
m=11