You can not solve for a as all of the numbers are unknown
First, you have to apply the order of operations.
Division and multiplication come first here and they go from left to right. So,
56/7 = 8
7*3 = 21
Then, the addition.
8 + 21 = 29.
So the value of your expression is 29.
We can use substitution or elimination
Let’s use substitution
Make slope intercept equation for the first equation
Y = -x + 5
Now plug in the y value for the second equation
-5x - 4(-x + 5) = -18
-5x + 4x - 20 = -18
-1x = 2, x = -2
There is one solution
