find the values of a and b such that x^2 +2x - 7 = ( x + a)^2 + b

Cost of 7 gallons=$24.50

Cost of 1 gallon=24.50/7=3.5

Cost of 15 gallons=15*3.5=52.5

Cost of 15 gallons will be $52.5

The solution is in the following image

Here,

tip=18%of $32

tip=(18/100)*32

=0.18*32

=$5.76

Total payment=32+5.76=$37.76

The wood before starting =12 feet

Left wood=6 feet

Wood used till now=12-6=6 feet

Picture frame built till now= 6/(3/4)

=8 pieces

Therefore, till now 8 pieces have been made.

The answer is in the image 

Area of rectangle= L*b

here,

L=12.4 cm

b= 8.8 cm

A= L*b

= 12.4 * 8.8 = 109.12 cm^2

Given height of gymnasium is 5/6 height of 30 foot ball

therefore height of gymnasium=5/6 * 30

=25 feet

Cost of 6 gallons =$15

Cost of 1 gallon =15/6

                           =$2.5

Cost of 7 gallons=$2.5 * 7

                           =$17.5

The answer is in the image 

Total fabric purchased = 1 1/4 = 5/4

Fabric used = 3/4

Fabric left = 5/4 - 3/4

                 = 2/4

                 =1/2 yard