All you really have to do is try to find the nearest fractions equal to 4/12
Step-by-step explanation:
I recommed that you use fraction strips. If you do not have these, you can grab a blank piece of paper, a ruler, and a pencil. Make the spaces ruler length apart. Do it until you get to the top. Cut these pieces and fold them all the way up to 12ths. Label them 1/2 to 1/12 but don't do the 11. This might help you a bit.
JK+KL=JL (5x-8)+7x-12=10x-2 (add common terms together) 12x-20=10x-2 (get the term with x alone on one side of the equation) 2x=18 (divide by 2 to get x alone) x=9