-2 3/7 × 1 3/4 = - 17/7 ×7/4 = -17/4=
= - 4 1/4
а) 63/50*100%=26%
б) 200/80*100%=150%
в) х/12=17/30
30/12=17/х
2.5=17/х
2.5*х=17
х=17/2.5
х=6.8