a)
[tex]30y + 5 = 4(9 + 5y)[/tex]
[tex]30y + 5 = 36 + 20y[/tex]
[tex]30y - 20y = 36 - 5[/tex]
[tex]10y = 31[/tex]
[tex]y = \frac{31}{10} = 3 \frac{1}{10} [/tex]
b)
[tex] - 5x + 12 + x = 2x - 12[/tex]
[tex] - 4x - 2x = - 12 - 12[/tex]
[tex] - 6x = - 24[/tex]
[tex]x = - 24 \div ( - 6) = 4[/tex]
c)
[tex]0.1x + 5 = 0.3[/tex]
[tex] \frac{1}{10} x = 0.3 - 5[/tex]
[tex] \frac{1}{10} x = - 4.7[/tex]
[tex]x = - 4.7 \times 10 = - 47[/tex]
