What are the three ways that causes variation of traits

1) Crossing over, pairing the genetics of a chromosome
2) During meiosis, the division of sex cells, genetic material in the form of chromosomes sorts itself randomly between cells
3) mutations in the cell can be caused, either positive or negative results

3x+22+5x-17=77
8x+5=77
8x=72
X=9
Angle ABD
3(9)+22
27+22=49
Angle DBC
5(9)-17
45-17=28