When multiplying two equations like this, you need to distribute. Distribute each term to get <span><span><span><span><span><span>3<span>x</span></span></span></span></span></span></span> <span><span><span><span><span>+ <span>3</span></span></span></span></span></span><span><span><span><span>− <span>26</span></span></span></span></span><span><span><span>−<span>14</span></span></span></span><span><span>−<span>15</span></span></span><span>−<span>24x</span></span>+<span>3</span>
This is through using a trigonometry calculator I forgot how to set it up tbh.
Hope this helps ;)
For extra info Angle C = 33.690067525979785.
They add up to 90 which added with the right angle of 90 means the interior angles add to 180 meaning it is in fact correct because a triangle is always 180 inside.