Final answer:
The highest temperature recorded can be found by adding 15°F to the lowest temperature of -28°F.
Step-by-step explanation:
To find the highest temperature given that the lowest temperature recorded was -28°F and the warmest temperature was 15°F higher, we can write an expression and solve it. Let's let x represent the lowest temperature. The expression can be written as x + 15. To solve for the highest temperature, we substitute -28°F for x in the expression:
Highest temperature = -28°F + 15°F = -13°F
Therefore, the highest temperature recorded is -13°F.