5+2a+4= 5+2a+4= 5+2a+4=
Given that in the exercise there is only one addition operation, the substitution property can be used:
5+4+2a= 5+4+2a= 5+4+2a=
We solve the exercise from left to right:
5+4=9 5+4=9 5+4=9
Now we obtain:
2a+9 2a+9 2a+9