Question 947756

let the total number of pupils in the class be {{{x}}}

{{{x=boys+girls}}}
if a class has {{{21}}} boys,

and the girls make up {{{(2/5)}}} of the class which means the girls make up {{{(2/5)x}}}, then


{{{x=21+(2/5)x}}} .........solve for {{{x}}}

{{{x-(2/5)x=21}}}

{{{5x/5-(2x/5)=21}}}

{{{(5x-2x)/5=21}}}

{{{3x/5=21}}}

{{{3x=21*5}}}

{{{3x=105}}}

{{{x=105/3}}}

{{{x=35}}} -the total number of pupils in the class