36/60*X=30/60*(X+40)
The solution is X=200.
② Set the junior high school plan as X and the senior high school plan as Y..
X+Y=3000
20%*X+30%*Y=3780-3000
X= 1200 Y= 1800。
③ let wheat x corn y.
X+Y= 18
12% * X+ 10% Y = 20- 18
X= 10 Y=8。
④ Let Dennis spend Q and Carrefour spend W..
Q=300+(X-300)*80%
W=200+(X-200)*85%
The two companies use the same fees.
Q=W
300+(X-300)* 80% = 200+(X-200)* 85%
X=600
Please ask questions if you have any questions, and please adopt them if you have no questions! ! Thank you!