[tex]250-number\ of\ people\\\\\dfrac{2}{5}\ of\ the\ 250\ people\to\dfrac{2}{5}\cdot250=\dfrac{2}{1}\cdot50=100-number\ of\ girls\\\\\dfrac{3}{10}\ of\ the\ 250\ people\to\dfrac{3}{10}\cdot250=\dfrac{3}{1}\cdot25=75-number\ of\ boys\\\\100+75=175-number\ of\ girls\ and\ boys\\\\250-175=75-number\ of\ adults\\\\Answer:\ 75[/tex]
