Question 687069
Hint: x+3 = y is the same as y = x+3


So y and x+3 are the same.


This means we can replace 'y' in the second equation with 'x+3' to go from


3x+4y=7


to 


3x+4(x+3)=7


Now solve for x. Then use this solution for x to find the solution for y.