3) x : 4 3/8 = 1.5 : 1 5/16

х*15/16=1,5*4 3/8
15/16х=1,5*35/8
15/16х=1,5*4,375
15/16х=6,5625
16/15*15/16х=16/15*6,5625
х=16/15*65625/10000
х=4375/625
х=7