Answer:
The answer is: Jacob Johnson should cultivate 400 acres of corn and 100 acres of wheat.
Explanation:
x = corn acre ; y = wheat acre
Step 1:
x + y = 500
42x + 30y = 19,800
Step 2:
Multiply (x + y = 500) times -30 ; -30x - 30y = -15,000
Step 3:
42x + 30y = 19,800
-30x - 30y = -15,000
Step 4:
(42x - 30x) + (30y - 30y) = 19,800 - 15,000 ; 12x = 4,800
Step 5:
x = 4,800/12 ; x = 400
Step 6:
400 + y = 500 ; y = 100