Question 1158958

let Sally's age be {{{x}}} and Linda’s age {{{y}}}


if Sally is four times Linda’s age, we have

{{{x=4y}}} .....eq.1

if in {{{10}}} years’ time the sum of their ages will be {{{75}}}, we have

{{{(x+10)+(y+10)=75}}}
{{{x+10+y+10=75}}}
{{{x+y+20=75}}}
{{{x+y=75-20}}}
{{{x+y=55}}}.......eq.2

substitute {{{x}}} from eq.1

{{{4y+y=55}}}
{{{5y=55}}}
{{{y=11}}}

then

{{{x=4y}}} .....eq.1,substitute {{{y}}}

{{{x=4*11}}}

{{{x=44}}}


Sally  is {{{44}}} years old now.