[tex]a) \: 2y-5=7 \\ 2y = 7 + 5 \\ 2y = 12 \\ y = 6 \\ \\ 2 \times 6 - 5 = 7 \\ 12 - 5 = 7 \\ 7 = 7 \\ \\ b) \: 3a+8= -3 \\ 3a = - 3 - 8 \\ 3a = - 11 \\ a = - \frac{11}{3} = - 3 \frac{2}{3} \\ \\ 3 \times - \frac{11}{3} + 8 = - 3 \\ - 11 + 8 = - 3 \\ - 3 = - 3 \\ \\ c) \: 25-4x=9 \\ - 4x = 9 - 25 \\ - 4x = - 16 \\ x = 4 \\ \\ 25 - 4 \times 4 = 9 \\ 25 - 16 = 9 \\ 9 = 9[/tex]
