Can you pay the exact amount (no change ) of $20 by using seven $1, $5, and $10 bills?

eh, you're over

Step-by-step explanation:

1 x 7 = 7    ,    7 + 5 = 12    ,    12 + 10 = 22

2^y = ln 5, or   y(ln 2) = ln 5.   solving for y,   y = (ln 5) / (ln 2).   y=5

step-by-step explanation:

(sin 42)/31. = sinx)/37

sinx = 37 (sin42)/31

= 37× 0.66/31 = 0.787

x= 51.9

other angle opposite to y = 180-51.9-42

= 180- 93.9 =86.1

so

sin42)/31 = sin 86.1)/y

0.021 = 0.997 /y

y= 0.997/0.021 =47.47