He is incorrect because each number is in a different place and those different places are worth more or less than the other places
I can’t see the pic , im so sorry

Hey mate,
Attachment 3 is a right angle because a right angle makes a straight line ( 90 degree angle)
that's why it's a right angle
<h3>plz mark me as brainliest </h3>
Answer:
99
Step-by-step explanation:
You can solve it by Squaring/multiply 18 by itself and 15 by itself then subtract them both:
(18 × 18) - (15 × 15)
324 - 225
99
You could also do difference of two squares:
(x² - y²)
= (x + y) (x - y)
= (18 + 15) (18 - 15)
= (33) (3)
= 99
I can’t see it needs better lighting