Solve the system using substitution x+5y=0 3y+2x=-21

total amount spent on toll=$1.75 each(two in number i.e at two tolls)

                                              =1.75×2=$3.50

amount spent on gas station for filling up the gas =$ 28

suppose amount spent on two tolls and amount spent on gas station for filling the gas are two solution of an algebraic expression.

now , writing in terms of algebraic expression

⇒(x-3.50)(x-28)

⇒(x-7/2)(x-28)

⇒x(x-28)-7/2(x-28)

⇒x²-28 x-7/2 x-

⇒x²- +98

terms are, x²,-,98

coefficient of x²=1

coefficient of x= =-1/2×7×3×3×x

constant term=98=7×7×2

coefficients of the algebraic expression that represents the total cost of gas and tolls=-[coefficient of x]=63/2=28 [amount spent on gas] +3.50 [amount spent on toll]=$31.50