Write an equation in slope-intercept form for the line with slope
−23
and
y
-intercept
−4
.

This would be easy for you if you know what the slope intercept form is.
y = mx + b this is the formula. M is where you put the slope and b is where the y-intercept goes. Now let's plug the numbers in. 
The slope you said is -23 so that goes into the place of m. X is the variable. I'll give you an example. Say Mary put $100 into her bank account and every week she took 23 dollars. x would the number of weeks because it can change. 
So back to plugging the numbers in. This is what it will look like when we put -23 in. 
y = -23x + b. As we said above, b is the y-intercept. This is the point where the line on the graph crosses the vertical line, which is y. x is the horizontal line.
You said the y-intercept is -4 so the line crosses the vertical line at the point -4. 
Plug this number into our formula, 
y = -23x + -4. 
There you go! We are finished making our slope intercept form equation.
I hope you understood, and good luck to you in the future.