If you would like to multiply 5 1/2 * 2 4/5, you can do this using the following step:
5 1/2 * 2 4/5 = 11/2 * 14/5 = 77/5 = 15 2/5
The correct result would be 15 2/5.
If you would like to add 3.38 + 86.3 + 0.796, you can do this using the following step:
3.38 + 86.3 + 0.796 = 90.476
The correct result would be 90.476.