Answer:
4 minutes
Step-by-step explanation:
Carmella turns on her oven, which heats up at 80 degrees per minute. The temperature of her house, and therefore her oven, is 70 degrees. Let x be the number of minutes that it will take for her oven to reach 390 degrees.
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Her oven heats at 80 degrees per minute or 80x.
The goal is 390 degrees and the starting temperature is 70 degrees so:
80x + 70 = 390
subtract 70 from both sides:
80x + 70 - 70 = 390 - 70
80x = 320
divide both sides by 80:
80x/80 = 320/80
x = 4
so it will take 4 minutes for an oven to heat up to 390 degrees if the starting temperature is 70 degrees and the oven can heat 80 degrees per minute.