Hello, can someone please explain how to find these? Thank you so much from the bottom of my heart!

Add or subtract in each case. Write all fraction answers as mixed numbers. Place a space between the whole number and the fraction.

1: 5.8 + (-8.45)
2: -3/4 + 7/8
3: -13.62 - (-27.9)
4. -3 2/5 - 4 1/2