The whole bill is $31.99 that is 100%. You can use mental math to determine exatcly 15% from $31.99:
1. 15%=10%+5%
2. To find 10% from $31.99 you should simply divide $31.99 by ten. Thus, 10% from $31.99 is $3.199.
3. 5% is half of 10%, then 5% from $31.99 is $3.199:2=$1.5995.
4. 15% from $31.99 is $3.199+$1.5995=$4.7985≈$4.80.
Answer: correct choice is B.
For this case we have the following expression:

Applying distributive property to the terms within parentheses we have:

We add similar terms on both sides of equality considering that:
Equal signs are added and the same sign is placed.
Different signs are subtracted and the major sign is placed.

We add 7.5x to both sides of equality:

We subtract 72 from both sides of equality:

We divide between 3 on both sides of equality

ANswer:
Distributive property
Add similar terms
Equality property of the sum
Equality subtraction property
Equality property of the division
4x - 5y = -12
-x + 5y = 18
Add the equations together:
4x + -x = 3x
-5y + 5y = 0
-12 + 18 = 6
So now you have:
3x = 6
Divide both sides by 3:
X = 2
Now you have the value of x, replace x with 2 in one of the equations and solve for y:
4(2) -5y = -12
8 -5y = -12
Subtract 8 from both sides:
-5y = -20
Divide both sides by -5:
Y = 4
The solution is x = 2 and y = 4 which is written as (2,4)
Wait but that is a test don't you need to look at a book or something insteadt of waiting for the answers