If X is partly costant and partly varies with y, when y=40, X=150, and when y=54,x=192. find x when y=73
x = a y + k
150 = 40 a + k ... 192 = 54 a + k
... subtracting equations ... 42 = 14 a ... a = 3
... substituting ... 150 = 120 + k ... k = 30
x = 3 y + 30