a) x/y=3/4=k => x/3=y/4=k => x=3k, y=4k
2x+3y/4x+y=2*3k+3*4k/4*3k+4k= 6k+12k/12k+4k = 18k/16k =18/16= 9/8
b) x/y=7/9 => x/7=y/9=k => x=7k, y=9k
x+2y/3x+y = 7k+2*9k/3*7k+9k = 25k/30k= 25/30=5/6
c)x/2=y/5=k => x=2k, y=5k
7x-2y/x+4y=7*2k-2*5k/2k+4*5k=14k-10k/2k+20k=4k/22k=4/22=2/11
d) x/3=y/11=k=> x=3k, y=11k
10x-y/x+y=10*3k-11k/3k+11k=30k-11k/14k=19k/14k=19/14