#### Answer

There is a demand for approximately 3 desk lamps.

#### Work Step by Step

The demand equation is as follows:
$p=-x^2+15$
where, p = unit price and x = demand
The price is given as 7 dollars per pair.
Therefore, the equations becomes-
$7=-x^2+15$
Step 1: Subtract 15 from both sides of the equation
$7-15=-x^2$
$-8=-x^2$
Step 2: Divide both sides by $-1$
$8=x^2$
Step 3: use the square root property:
$±\sqrt 8=x$
$x= ±\sqrt{4\times2}$
$x= ±2\sqrt{2}$
$x= ±(2\times1.4142)$
$x=±2.8284$
Since the demand cannot be negative, there is a demand for approximately 3 desk lamps.