Question

the expression $-270 + 12x$ represents a submarine that began at a depth of 270 feet below sea level and ascended at a rate of 12 feet per minute. what was the depth of the submarine after 7 minutes?

select the correct answer below and, if necessary, fill in the answer box to complete your choice.

a. the submarine was blank feet below sea level after 7 minutes.

b. the submarine will have reached sea level after 7 minutes.

Explanation:

Step1: Identify the expression and variable

The expression is $-270 + 12x$, where $x$ represents the number of minutes. We need to find the depth after 7 minutes, so we substitute $x = 7$ into the expression.

Step2: Substitute the value of x

Substitute $x = 7$ into $-270 + 12x$:
\[

$$\begin{align*} -270 + 12\times7&=-270 + 84\\ &=-186 \end{align*}$$

\]
The negative sign indicates the depth is below sea level.

Answer:

A. The submarine was $\boldsymbol{186}$ feet below sea level after 7 minutes.