Question 16351
x=greater number
y=lesser number
the greater of 2 numbers is 7 more than the lesser
x=y+7
Three times the greater number is 5 more than 4 times the lesser number 
3x=5+4y
We will begin by substituting x=y+7 in the second equation;
3(y+7)=5+4y
3y+21=5+4y
3y-4y=5-21
-y=-16
y=16
Now we have what y =, so we plug it into the equation to find x,
x=y+7
x=16+7
x=23
We are done, we have both y and x;
x=23
y=16
Don't forget to check your answer!
hope you understand
=)