[tex] \frac{a}{3} = \frac{b}{4} = > a = \frac{3b}{4} [/tex]
[tex]2a + 3b = 54[/tex]
[tex]2 \times \frac{3b}{4} + 3b = 54[/tex]
[tex] \frac{3b}{2} + \frac{6b}{2} = \frac{54 \times 2}{2} [/tex]
[tex]9b = 54 \times 2[/tex]
[tex]b = \frac{54 \times 2}{9} = 6 \times 2 = 12[/tex]
[tex]a = \frac{3b}{4} = \frac{3 \times 12}{4} = 3 \times 3 = 9[/tex]
