At a T.I concert, the ratio of the number of girls to the number of boys is 2:7. If there are 250 more boys than girls, how many girls are at the concert?

g/b = 2/7

b = g+250

now just solve.

To solve this problem, we can set up a system of equations. Let's denote the number of girls as 'g' and the number of boys as 'b'.

According to the given information, the ratio of girls to boys is 2:7. We can express this as:

g/b = 2/7

It is also stated that there are 250 more boys than girls. This can be expressed as:

b = g + 250

Now we have a system of equations:

g/b = 2/7 (Equation 1)
b = g + 250 (Equation 2)

To solve for g, we can substitute Equation 2 into Equation 1:

g/(g + 250) = 2/7

To get rid of the fractions, we can cross-multiply:

7g = 2(g + 250)

Distribute the 2 on the right side:

7g = 2g + 500

Subtract 2g from both sides:

5g = 500

Finally, divide both sides by 5:

g = 100

Therefore, there are 100 girls at the T.I concert.