The answer and how to do it.

let x = orginal price of the shorts

$21 = x(100%-20%) * 1.05

$21 = x(80%) * 1.05

$21 = 0.8x * 1.05

Subtract 1.05 from both sides

$19.95 = 0.8x

Divide 0.8 from both sides

$24.9375 = x

So the orginal price of the shorts are about $24.94

step-by-step explanation:

solution:

→c= a b , that is product of a and b is possible only when when a is m × n matrix and b is n × p matrix.

that is, number of columns of a= number of rows of b.

so, size of matrix , c= a b is , if a = (m × n)matrix

b= (n × p)matrix

then a b = [ (m × n)matrix] ×[   (n × p)matrix ]

→→c= a b= [m × p ] matrix

→→size of product a b will be equal to = number of rows of a × number of columns of b