The farmer would get 30 lb of 18-16-2 fertilizer.
We can use a variation of the dilution formula to solve this problem.
V₁c₁ + V₂c₂ = V₃c₃
For N
5 lb × 11 + 25 lb × 19 = 30 lb × x
55 + 475 = 30x
x = 530/30 = 18
For PO₄
5 lb × 11 + 25 lb × 17 = 30 lb × y
55 + 425 = 30y
y = 480/30 = 16
For K
5 lb × 11 + 25 lb × 0 = 30 lb × z
55 + 0 = 30z
x = 55/30 = 2
The farmer would get 30 lb of 18-16-2 fertilizer.