The difference between the coefficients 7 and 3 is 4, so one solution is y = 1, x = -1. Then the remaining solutions will be of the form x = -7n-1 y = 3n+1 for some integer n.
_____ Some of the solutions are (for n=0, -1, -2, 1, 2) (x, y) = (-1, 1), (6, -2), (13, -5), (-8, 4), (-15, 7)
Since 40%=40/100=4/10, we can divide 11 by 10 and multiply that by 4 to get the weight gained, which is 1.1*4=4.4. The weight gained paired with the starting weight = 10+4.4=14.4
