you have to do mutiplication. how do you know that you have to do mutiplcation because the (of) it means times. so 26 2.21 = 0.5746
2.21/x=100/26
(2.21/x)x=(100/26)x
2.21=3.8461538461538x
(3.8461538461538) to get x
2.21/3.8461538461538=x
0.5746=x
x=0.5746
