Compare and order 5.2, -5.6, 3 9/10, the square root of 21? ?

I would first suggest turning them all to one thing, like all decimals, or fractions. I chose decimals.

5.2, -5.6, 3.9, √21. To solve the square root, you have to simplify it. There is the square root of 3, times the square root of 7 which gets 21. These can't be simplified, so we can't simplify through that. But, the closest whole number that is a square root is 16. You can check by multiplying the same number together twice. Doing this will get you about 4.58

5.2, -5.6, 3.9, and ≈ 4.58. This is a simple ordering problem now.

It ends up as -5.6, 3 9/10, √21, 5.2

There are 2 decimals, one negative. There is one square root, and one mixed number. The square root is an infinite decimal when simplified

Hope this helps! ~Malachi