5 tens x 3 ones = [ ] tens

Please help​

Describe in detail how you would construct a 95% confidence interval for a set of 30 data points whose mean is 20 and population standard deviation is 3. be sure to show that you know the formula and how to plug into it. also, clearly state the margin of error.

Find the solution of this system of equation -7x+y=-20 9x-3y=36

If you could answer these your a life saver