They are both right angles. If they are vertical they are congruent, and if they are supplementary they add to 180. Only two right angles would satisfy both conditions.
The answer is d the last one
Three unknowns requires three equations to solve . . .
1) n + d + q = 30
2) d = 2n
3) (0.05)n + (0.10)d + (0.25)q = 5.50
* plug 2) into 1) and solve for q
n + 2n + q = 30
3n + q = 30
q = 30 - 3n
* now we have variables d and q expressed in terms of n, so we plug those equations into 3) and solve for n . . .
0.05n + 0.10(2n) + 0.25(30 - 3n) = 5.50
0.05n + 0.20n + 7.50 - 0.75n = 5.50
(0.05 + 0.20 - 0.75)n + 7.50 = 5.50
-0.50n + 7.50 = 5.50
-0.50n = 5.50 - 7.50
-0.50n = -2.00
n = -2.00/-0.50 = 4
d = 2n = 2(4) = 8
q = 30 - 3n = 30 - 3(4) = 30 - 12 = 18
The answer is . . .
n = 4 nickels
d = 8 dimes
q = 18 quarters
. . . for a total of (4 + 8 + 18) = 30 coins
. . . 8 dimes is twice 4 nickels
. . . $0.05(4) + $0.10(8) + $0.25(18) = $5.50
U = 3 hours since 3 is the least amount of time it would take underwater. Hope this helped
