so what we want to do is make the function equal to the value of 3, so that we can solve for x

so we have

3=(sqaure root) x+4

Now, how do we solve for x since we have that big annoying square root? We simply square both sides. Squaring both sides will cancel the square root, leaving

9=x+4

Now, simple isolate x by subtracting 4 on both sides

9-4=x+4-4

so x=5

Now, just to check, plug x=5 back into the original equation. Does it equal 3? YES!