Divide everything by 4 getting:
7y=3x+21
then get all of the variables on one side by subtracting 3x:
7y-3x=21
Greatest Common Factor. let's go over that. GCF of 6 and 12 would be 6 because 6 goes into 6, 1 times and 6 goes into 12, 2 times. . and it is the largest. so first you see if the lower number can go directly into the higher number. So 28a^2 b^2 c^2, is made of 14abc× 2abc. so you can say 14abc goes into 28a2b2c2, 2abc times. therefore 14abc is the largest factor.
By solving for x you get x=6
Can you please complete your question
