Question 502959
Let
Total number of Boys = b
Total number of Girls = g
the number of boys is 16 less than twice the number of girls
b=2g-16........(1)
There are 68 students altogether 
b + g = 68
g = 68 - b 
Put the value of b in above equation
g = 68 - (2g-16)
g = 68 - 2g + 16
g + 2g = 68 + 16
3g = 84
g = 84/3
g = 28
There are 28 girls in grade eight
And 
Boys = Total sutudents -  Grils
Boys = 68 - 28
Boys = 40