if S1={1,2,3,4,5,6,7,8,9,10,11,12,13,1 4,15,16,17,18,19,20}, S2={a, b,c, d}, S3={b, d,e, f}.The number of elements of (S1×S2) U (S1×S3) is​

77

step-by-step explanation:

step-by-step explanation:

total income = price of one ticket   *   number of tickets sold

  y                 =     4                                   x

so the equation is y=4x     with x≥0   because number of tickets sold can not be negative

thus the equation is a semi -line with an end point at

(0,0)

passing through :

x=1     y=4(1) = 4   so through (1,4)