Roberto overtakes Juanita at the rate of (7.7 mi)/(11 h) = 0.7 mi/h. This is the difference in their speeds. The sum of their speeds is (7.7 mi)/1 h) = 7.7 mi/h.
Roberto walks at the rate (7.7 + 0.7)/2 = 4.2 mi/h.
Juanita walks at the rate 4.2 - 0.7 = 3.5 mi/h.
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In a "sum and diference" problem, one solution is half the total of the sum and difference. If we let R and J be the respective speeds of Roberto and Juanita, we have
R + J = total speed
R - J = difference speed
Adding these two equations, we have
2R = (total speed + difference speed)
R = (total speed + difference speed)2 . . . . . as computed above
That figure obviously doesn't go with this problem. It doesn't matter; this is triangle ABC labeled the usual way.
c = 10, B = 35°, C = 65°
We have two angles and a side. The third angle is obviously
A = 180° - 35°- 65° = 80°
The remaining sides are given by the Law of Sines,



Answer: A=80°, a=10.9, b=6.3, third choice
If it takes .1 hours to walk 2/6 miles, then it takes one hour to walk 20/6 miles.
20/6 miles = 3.33 miles
So that is 3.33 miles per hour.