My daughter got this question and I cannot solve it - or even give her direction. It appears there in not enough information.
the number of equilateral triangles of side 1 into which an equilateral triangle of side n can be divided? ( n is a whole number)
Your daughter might like to think about two ways of tackling this ...
Approach A
Draw a triangle of side 2, and fit four unit triangles into it.
Extend that picture to a triangle of side 3: how many new unit triangles of side one can you fit into the newly added strip (the trapezoid 2 units along the top, 3 along the bottom)? So how many triangle fit into the whole triangle?
Extend that picture to a triangle of side 4: how many new unit triangles of side one can you fit into the newly added strip this time? So how many in the whole triangle?
What's the pattern?
Approach B
Think about areas. What is area of a square of side 2 compared with the area of a unit square? What is area of an equilateral triangle of side 2 compared with the area of a unit triangle? Why can you know the ratio of the triangles without calculating the actual areas?
What is area of an equilateral triangle of side $n$ compared with the area of a unit triangle?