Question 312379
Let B be the boys' scores, G be the girls' scores.
{{{(B+G)/30=80}}}
1.{{{B+G=2400}}}
.
.
{{{G/20=85}}}
2.{{{G=1700}}}
Then from eq. 1,
{{{B+G=2400}}}
{{{B+1700=2400}}}
{{{B=700}}}
Since there are 10 boys, then
{{{Y=700/10=70}}}
The boys had an average of 70 on the test.