Answer:
Step-by-step explanation:
r = 21/42 = 1/2 ( also 10.5 / 21 = 1/2)
This is a Geometric Sequence with first term 42 and common ratio 1/2.
8/12-9/12 multiply 4 by 3 and then multiply 3 by 3 and you'll get 9/12
Pythagorean theorem should help with your question so try that and let me know if you don't understand it
