[tex]5a(a - 3) - 2( {a}^{2} - a) = \\ = 5a \times a - 5a \times 3 - 2 \times {a}^{2} + 2 \times a = \\ = 5 {a}^{2} - 15a - 2 {a}^{2} + 2a = \\ = 3 {a}^{2} - 13a[/tex]
