Question 306221
Let A and B bet the numbers.
1.{{{A+B=45}}}
2.{{{3A+7B=115}}}
From eq. 1,
{{{A+B=45}}}
{{{A=45-B}}}
Substitute into eq. 2,
{{{3A+7B=115}}}
{{{3(45-B)+7B=115}}}
{{{135-3B+7B=115}}
{{{4B=-20}}}
{{{highlight( B=-5)}}}
Then from eq. 1,
{{{A=45-B}}}
{{{A=45-(-5)}}}
{{{highlight( A=50)}}}