Question

There are 23 students in a karate class. The number of girls is less than twice the number of boys. Write two systems of equations.

Answer 1

Let's call the girls "x" and the boys "y".

first equation is this one:
There are 23 students in a karate class.

this we would write:
x+y=23

and the second equation can be found from this sentence:

The number of girls is less than twice the number of boys

which means:
x<2y.

Now, that's an inequality, but it's all we can do here, since the question doesn't tell us anything more - also, we can's solve it exactly.

we could say, for example that it's less by 1, then it would be:
x-1=2y.

but the question doesn't say by how much less!