[tex] \frac{3a}{2b} = \frac{3}{5} [/tex]
[tex]3a \times 5 = 2b \times 3[/tex]
[tex]15a = 6b[/tex]
[tex]a = \frac{6b}{15} [/tex]
[tex]a = \frac{2b}{5} [/tex]
[tex]a + b = 210[/tex]
[tex] \frac{2b}{5} + b = 210 \: | \times 5[/tex]
[tex]2b + 5b =1050[/tex]
[tex]7b = 1050[/tex]
[tex]b = \frac{1050}{7} [/tex]
[tex]b = 150[/tex]
[tex]a = \frac{2b}{5} [/tex]
[tex]a = \frac{2 \times 150}{5} [/tex]
[tex]a = \frac{300}{5} [/tex]
[tex]a = 60[/tex]