Keep in mind that f(x) means the same thing as y so...
y = 2x + 3
To find the inverse operation you switch the places of x and y like so...
x = 2y + 3
Now you must solve for y. To start off you must subtract 3 to both sides.
x - 3 = 2y + 3 - 3
x - 3 = 2y
Now divide 2 to both sides to completely isolate y
(x - 3) / 2 = 2y / 2
= y
OR
= y
Hope this helped!
~Just a girl in love with Shawn Mendes