Answer:
9/5
Step-by-step explanation:
<h2>
Explanation:</h2>
In physics, work is defined force that causes displacement. So this can be expressed by the following equation:

Where:

The force can be found as:

And for the displacement:

The force (weight) is down and the displacement is up, then the work must be negative. So:

<span>Select one equation and solve it for one of its variables.
In the other equation, substitute for the variable just solved.
Solve the new equation.
<span>Substitute the value found into any equation involving both variables and solve for the other variable. </span></span>
Answer:
t > 1380
Step-by-step explanation:
Subtract 7200 from both sides
10t + 7200 - 7200 > 21000 - 7200
Simplify
10t > 13800
Divide both sides by 10
10t/10 > 13800/10
Simplify
t > 1380