How do you solve for a variable?

I was just wondering how do you solve for a variable in MATHCAD. I have a function defined as

h(v,k,c):=(k/c)(v/c)^(k−1)exp(−(v/c)^(k))

This is a weibull distribution fucntion. k and c are already defined constants k = 1.5 and c = 15. I take the derivative

dh(v,k,c):=(d/dv)h(v,k,c)

I want to set it to zero and solve for v but when I set dh(v,k,c)=0 I get a 'variable is undefined error'. Anyone know how to set the equation equal to zero and solve for v?