The two rectangles below have the same height-to-width ratio. which is the value of w?

We know that
if the two rectangles have the same height-to-width ratio
so
height-to-width ratio larger rectangle
21/34---> equation 1
height-to-width ratio smaller rectangle
10/w> equation 2

equate equation 1 and equation 2

21/34=10/w> 21*w=34*10> w=34*10/21> w=16.19

the answer is
w=16.19