a)
X : 0,25 + X x 11 = 24
<=> X : 1/4 + X x 11 = 24
<=> X x 4 + X x 11 = 24
=> X x ( 4 + 11 ) = 24
=> X x 15 = 24
=> X = 1,6
b)
X x 8,01 - X : 100 = 38
<=> X x 8,01 - X : 1/100 = 38
<=> X x 8,01 - X x 0,01 = 38
=> X x ( 8,01 - 0,01 ) = 38
=> X x 8 = 38
=> x = 4,75