Let the answer be x.
Hence, f = x is the answer.
Read and understand given problem situations.
Develop and use the strategy: Draw a diagram.
Plan and complete alternative approaches to solving problems.
Solve real-world problems using selected strategies as part of a plan.
Answer:
if you want to sketch the trapezoid you will also need other dimensions like height and the length of the parallel sides
Estimate:
Bill = $20 approximately.
5% tax on $20 = 20/20=$1
20 % on ($20) = $4
Total cost = $20+1+4 = $25
Total bill = $25 approximately.
Exact calculations
bill = 19.68
tax 5% = 0.98
Tip 20% of original = 3.94
Total bill = 19.68+0.98+3.94 = 24.60
Given:

He does mistake in the order of giving preference.
We should give preference in the order, division, multiplication, addition, subtraction.
But, he gave the first preferrence to the subtraction.
72-8=64
Next, he used division
64/2=32
Next he adds 32 with 8.
So, he gets 50.
But the actual simplification is,
Simplifying we get,

Hence, the correct value of the expression is 86.