The correct answer is 1 7/15.
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.
It is a right, isosceles triangle.
It should be (2x-3)x(3x+2)
Answer:
30 tens
90 is the greatest number of tens