In how many ways can you select two people from a group of 15 if the order of selection is not important?

105 ways

Step-by-step explanation:

Because the order of selection does not matter, we know that we will be using a combination instead of a permutation.

₁₅C₂ = 15! / (2! * 13!)

= 15 * 14 * ... * 2 * 1 / 2 * 1 * 13 * 12 * ... * 2 * 1

= 15 * 14 / 2 * 1 (The 13! cancels out)

= 105

system of linear equation

step-by-step explanation:

as given in the data

a= 20 , b= -12

let us suppose that it is a straight line equation

now we know the formula for the system of linear equation

b= ma + c )

here m is slope of a straight line which is equal to formula

m=   (ii)

and here c is a constant

now putting the value of a and b in equation (ii)

m=

m=

putting the value of a,b and m in equation (i) gives us

-12 = + c

-12=-12 + c

adding 12 to both sides

-12 +12 = -12 +12 +c

0 =c

or c=0

as the value of the constant is zero which gives us that it is a linear equation and this order pair satisfies the system of linear equations.