Do you have a picture to go with this? I can't help without the picture :(
-(4/5)*(3/7)*(15/16)*(-14/9) [two negatives make one positive]
=(4*3*15*14)/(5*7*16*9) [simplify 4/16]
=(3*15*14)/(5*7*4*9)
=(3*3*14)/(7*4*9)
=(14)/(7*4)
=(2)/(4)
=1/2
Try to subtitute y with 3x - 7
15x - 5y = 14
15x - 5(3x - 7) = 14
15x - 15x + 35 = 14
35 ≠ 14
The equation system doesn't have any solution