[tex]a \div 100 \div 10 \times 3 + 390 = 510[/tex]
[tex] \frac{1}{100}a \times \frac{1}{10} \times 3 + 390 = 510 [/tex]
[tex] \frac{3}{1000}a + 390 = 510 [/tex]
[tex]3a + 390000 = 510000[/tex]
[tex]3a = 510000 - 390000[/tex]
[tex]3a = 120000[/tex]
[tex]a = 40000[/tex]
