So this is going to be using proportions, which in this case is going to be [tex] \frac{18}{21} =\frac{25}{x} [/tex]
Firstly, cross-multiply to get [tex] 18x=525 [/tex]
Next, just divide 18 on both sides, and your answer will be [tex] x=29.2 [/tex] , or the last option.
