Can someone me and show how to do it

If I were you I would disregard the formula they have laid out of you on your sheet. First combine all of the angles together. Remember that this is equal to 180 degrees. You should get 5x-5=180. Now simplify the equation. Add -5 to both sides to start with. Now you have 5x=185. Next divide both sides by 5. You should have x= 37 at this point. Now substitue in 37 in place of all the x's in the equation. Before doing this, make sure you have identified the largest angle, in this case it is 2x+15. Multiply 2 times 37 to get 74 and add 15 to get 89. This should look like 2(37)+15=89.
This leaves you with an angle measurement of 89 degrees. I hope this helps you!