1.A principal of $5000 was invested in a savings account for 4 years. If the interest earned for the period was $400, what was the interest rate?

2.¨C3(10x ¨C 3) + 10(3x ¨C 3) = x ¨C 7

3.Solve and graph the solution set.

To answer these questions, let's go through each one step by step.

1. To find the interest rate, we need to use the formula for simple interest: Interest = Principal * Rate * Time. In this case, we know the principal is $5000, the interest earned is $400, and the time is 4 years. Plugging in these values, we get:

$400 = $5000 * Rate * 4

To find the interest rate, we can divide both sides of the equation by ($5000 * 4):

$400 / ($5000 * 4) = Rate

Simplifying the right side, we get:

Rate = 0.02 = 2%

Therefore, the interest rate is 2%.

2. This is a algebraic equation, and we can solve it step by step:

- Distribute the terms:
-3(10x - 3) + 10(3x - 3) = x - 7

Simplifying the equation, we have:
-30x + 9 + 30x - 30 = x - 7

Combine like terms:
-30x + 30x + 9 - 30 = x - 7

Simplify further:
-21 = x - 7

Add 7 to both sides:
-21 + 7 = x - 7 + 7

Simplify:
-14 = x

So, the solution to the equation is x = -14.

3. To solve and graph the solution set, we need to have an inequality or equation given to us. If you provide us with a specific inequality or equation, we can help you solve it and graph the solution set.