The temperature of the substance at 10am  =  63.95°F
Let the temperature at 10 am be x
The temperature changes by −8.7°F from 10 a.m. to 1 p.m
The temperature at 1 pm = x  -  8.7
At 5 p.m., the temperature is 33.5°F
The temperature at 5 pm = 33.5°F
The temperature at 5 pm is 2/3 of what the temperature was at 1 p.m
[tex]33.5 = \frac{2}{3} ( x-8.7 )[/tex]
Solve for x
3(33.5)  =  2(x  -  8.7)
110.5  =  2x  -  17.4
2x  =  110.5 +  17.4
2x  =  127.9
x  =  127.9/2
x  =  63.95°F
The temperature of the substance at 10am =  63.95°F
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