Let n = minutes since 12:00 pm when Malory catches up to Dori.
Dori travels
(50 steps/min)*(n minutes) = 50n steps
Malory begins walking at 12:20 pm, so she walks for (n - 20) minutes. She travels
(90 steps/min)*(n - 20 min) = 90n - 1800 steps
Equate the steps traveled by Dori and Malory.
90n - 1800 = 50n
40n = 1800
n = 45 min
The time corresponding to n = 45 min is 12:45 pm
Answer: 12:45 pm
0.10d + 0.25q = 3.55
q = d + 3
0.10d + 0.25(d + 3) = 3.55
0.10d + 0.25d + 0.75 = 3.55
0.10d + 0.25d = 3.55 - 0.75
0.35d = 2.80
d = 2.80/0.35
d = 8.....8 dimes
q = d + 3
q = 8 + 3
q = 11 <=== 11 quarters