How many gallons of a plant food that is 6% nitrogen must be continued with another plant food that is 30% nitrogen to make 10 gal of a plant foo that is 21% nitrogen

Solution:
1. Let x be the gallons of 6% nitrogen plant food.
2. Then 10 - x will be the gallons of 30% nitrogen plant food.
3. The equation representing the total nitrogen content is:
0.06x + 0.30(10 - x) = 0.21 \times 10
4. Simplify the equation:
0.06x + 3 - 0.30x = 2.1
5. Combine like terms:
3 - 0.24x = 2.1
6. Isolate x:
0.9 = 0.24x
x = \frac{0.9}{0.24}
x = 3.75
7. Thus, 10 - x = 10 - 3.75 = 6.25.

The mixture requires:
- 3.75 gallons of 6% nitrogen plant food
- 6.25 gallons of 30% nitrogen plant food.