# Basic Supply and Demand Question [closed]

Suppose that the quantity supplied S and the quantity demanded D for the price p of t-shirts are given by the following functions

S(p) = −800 + 50p

D(p) = 1900−40p

Determine the prices for which the demand is greater than the supply.

I'm not sure how to solve this problem on mathematica, I'm new to the program so please bear with me.

• The expectation, in this forum, is that some effort will be expended and some code shown. If you are not able to get that far, discussion with instructor/TA and consultation with any basic resource for the Wolfram Language really need to take place. Bringing questions to a large open forum requires meeting the minimum requirements of that forum. – Daniel Lichtblau Nov 17 '18 at 16:09
• I'm voting to close this question as off-topic because the OP asking us to do his/her homework without displaying any prior effort. – m_goldberg Nov 18 '18 at 7:49

Welcome! Here's a quick way to solve this inequality:

Reduce[1900 - 40 p ≥ -800 + 50 p, p]


Then hit Shift-Enter to evaluate it. Output is:

p ≤ 30


In an earlier question you asked how to plot the supply and demand equations. You really don't need Mathematica to solve this, just simple algebra.

1900 - 40p ≥ -800 + 50p (* Add 800 to both sides *)
2700 - 40p ≥ 50p (* Add 40p to both sides *)
2700 ≥ 90p (* Divide both sides by 90 *)
30 ≥ p

• To my surprise, someone voted this answer down. I think Rohit is absolutely right with his solution. Things like this should be done with pen and paper. Pressing some keys of Mathematica does not contribute anything to a better understanding of what is going on. – Fred Simons Nov 17 '18 at 17:36
• @FredSimons Thanks. I was also surprised by the downvote. Maybe it was because it did not exactly answer the OP's question "how to solve this problem on mathematica". Perhaps a comment should be mandatory for any downvote on MSE? That feedback would certainly help me to improve the quality of my answers, especially since I am relatively new to MSE. – Rohit Namjoshi Nov 17 '18 at 18:03