Answer:
$42.09
Step-by-step explanation:
1. multiply the cost per gallon (3.45) by the gallons purchased (12.2)
3.45*12.2 = 42.09
Rahul use addition property of equality in step 2.
Solution:
The image of the question is attached below.
Step 1:

combine like terms together.

To make the denominator same multiply and divide 2x by 5.
Step 2:

By addition property of equality, add
on both side of the equation.

Step 3:

Step 4:
Multiply by
on both side of the equation.

Hence Rahul use addition property of equality in step 2.
Total number of outcomes of 7 from 10 = 10*9*8 / 3*2*1 = 120
probability of each outcoe is 0.85^7* (0.15)^(3) = 0.0010819
Required probability = 120 * 0.0010819 = 0.1298