X * 41,3 + x * 57,7 + x = 68

a, X x 41,3 + X x 57,7 + X= 68
b, $\frac{13 + x}{20} = \frac{3}{4}$
c, 70 $\div$ x $-$ 13 $\div$ x $-$ 2 $\div$ x = 5