Answer: 64 gallons
Explanation:
Let he mixed x gallons of 25%-concentrated teal dye with 16 gallon of 15%-concentrated teal dye to make 23%-concentrated teal dye.
Thus, the total quantity of the resultant dye = (16+x) gallon
Also,
The concentration of 25%-concentrated teal dye + the concentration of 15%-concentrated teal dye = The concentration of 23%-concentrated teal dye.
⇒ 25 % of x + 15 % of 16 = 23 % ( x + 16 )
⇒ 25 of x + 15 of 16 = 23 ( x + 16 )
⇒ 25 x + 15 × 16 = 23 x + 23 × 16
⇒ 25 x + 240 = 23 x + 368
⇒ 25 x + 240 - 23 x = 368
⇒ 2 x = 368 - 240
⇒ 2 x = 128
⇒ x = 64
Hence, the quantity of 25%-concentrated teal dye = 64 gallons