A class has 49 students. The ratio of boys to girls is 5:2. If x girls join the class, what is the new ratio of boys to girls?

The total number of students is 49.
The initial ratio of boys to girls is $5:2$.
The total parts in the ratio are $5 + 2 = 7$.
Number of boys = $\frac{5}{7} \times 49 = 5 \times 7 = 35$ boys.
Number of girls = $\frac{2}{7} \times 49 = 2 \times 7 = 14$ girls.

Let $x$ be the number of girls required to join.