A farmer has 1,200 acres of land on which he grows corn, wheat, and soybeans. It costs $45 per acre to grow corn, $60 for wheat, and $50 for soybeans. Because of market demand he will grow twice as many acres of wheat as of corn. He has allocated $63,750 for the cost of growing his crops. How many acres of each crop should he plant?

Let c, w, and s be the acres of the respective crops to be planted.

c=corn, w=wheat, s=soybean

We are told he has 1200 acres to plant.

Therefore, c+w+s=1200

One condition is that there is twice as much wheat as corn, 2c=w

The final equation is the cost, 45c+60w+50s=63,750

Now, you have three equations and three unknowns.

Solve using substitution or elimination. The condition 2c=w helps simplify it down to two equations easy enough.