Tính nhanh
a) \(\frac{3,06:7,5+3,4\text{x}0,38}{19-2,6\text{x}0,5}x\frac{\left(1,6-1-0,6\right)x\left(2,29-0,76\right)}{1,6+2,53}\)=
b) \(\frac{17,8\text{x}3,7-7,8\text{x}4,8+5,7\text{x}17,8-4,2\text{x}7,8}{11,2+12,3+13,4-12,6-11,5-10,4}=\)
Tìm X
x . 4 - x : 4 - 24,7 = 190,48 : 2