Step-by-step explanation:
If two lines are mutually perpendicular and going across each other then they will form maximum FOUR 90° angles.
AB is perpendicular to CD. So, FOUR 90° angles will be formed by their intersection.
23 Answer: 
<u>Step-by-step explanation:</u>


24 Answer: 
<u>Step-by-step explanation:</u>

25 Answer: n=7
<u>Step-by-step explanation:</u>

Answer:
-12 and 3
Step-by-step explanation:
-12x3= -36
-12+3= -9
7+9=16
Step-by-step explanation:
let us add the numbers step by step:
Just add the numbers like this [1+3,2+4,3+5,4+6,5+7,6+8,7+9…]
you get the answer 7+9=16