The temperature is 8*F. It is expected to fall 5* each hour for the next several hours. In how many hours will the temperature be -7*F?

a.
8 - 5x = -7; 3 hours
c.
8 + 5x = -7; -3 hours
b.
5x - 8 = -7; 1/5 hour (or 12 min)
d.
5x + 8 = -7; - 3 hours

Question

The temperature is 8*F.  It is expected to fall 5* each hour for the next several hours.  In how many hours will the temperature be -7*F?

a.
8 - 5x = -7;  3 hours
c.
8 + 5x = -7;  -3 hours
b.
5x - 8 = -7;  1/5 hour (or 12 min)
d.
5x + 8 = -7;  - 3 hours

phi · Answer

Looking at the answers, cross off any "negative hours".  We expect the answer to be "it will take some positive number of hours"  (negative hours does not make sense)

next, of those answer choices left,  use the "x" value they give in the equation they give.  In other words,  erase the x in the equation and put in the number they give for x.
Then simplify the equation to see if both sides are equal.  If so, that is the answer.

triciaal · Answer

|dw:1434935097110:dw|