proportion

18/14 equals 7/x.

Cross multiplying we get 91=18x

x=91/18

Suppose s and t are directly proportional. If s=14 when t=18, what is s  when t=7?

 

14 / 18 = s / 7      s = (14 * 7) / 18

s = kt    k = proportionality konstant

14 = k(18)

k = 14/18 = 7/9

 

sooo    s = 7/9 t

            s = 7/9 (7)

               = 49/9