Answer:
9.9
Step-by-step explanation:

Maria got 21 correct.
Number wrong = Total - Number right
y = 25 - 21
y = 4
Maria got 4 wrong.
Hope this helps!
Answer:
502.4 mm^2
Step-by-step explanation:
First find the area of the larger circle, and then that of the smaller one.
Then subtract the latter (2nd) area from the first.
larger circle area smaller circle area
------------------------- ---------------------------
3.14(14 mm)^2 3.14(6 mm)^ 2
This comes out to 3.14[14^2 - 6^2] mm^ 2 = 3.14[196 - 36] mm^2, or
3.14(160 mm^2) = 502.4 mm^2
The area of the metal washer is 502.4 mm^2.