Can someone check my work for me again! I really appreicate it, I'm not the best at this.

(1/3)x+(3/4)x = 13
(4/12)+(9/12)x = 13
(13/12)x = 13
x = 13/(13/12)= 12

Your answer is right. :-)

1/3 * 12 + 3/4 * 12 = 13
4 + 9 = 13