[tex] \frac{a}{b} = \frac{2}{5} [/tex]
[tex]a-b=-21[/tex]
[tex]5*a=2*b[/tex]
[tex]a= \frac{2b}{5} [/tex]
[tex] \frac{2b}{5} -b=-21[/tex]
[tex] \frac{2b-5b}{5} =-21[/tex]
[tex]-3b=-21*5[/tex]
[tex]-3b=-105[/tex]
[tex]b= \frac{105}{3} =35[/tex]
[tex]a= \frac{2b}{5} [/tex]
[tex]a= \frac{2*35}{5} = \frac{70}{5} =14[/tex]
[tex]a*b=14*35=490[/tex]
