Explanation
Step 1
Let x represents the number of shirts
then
Option 1
One option is to pay Anita's Tees a $25 setup fee and then buy the shirts for $5 each
[tex]Cost_1=25+5x[/tex]and, Another option is to go to City Printing, paying $30 for a setup fee and an additional $4 per shirt
[tex]\text{Cost}_2=30+4x[/tex]now, there is a value for x, that makes cost1=cost 2, Hence
[tex]25+5x=30+4x\text{ Equation(1)}[/tex]Step 2
solve the equation
[tex]\begin{gathered} 25+5x=30+4x\text{ Equation(1)} \\ subtract\text{ 4x in both sides} \\ 25+5x-4x=30+4x-4x \\ 25+x=30 \\ \text{subtract 25 in both sides} \\ 25+x-25=30-25 \\ x=5 \end{gathered}[/tex]so, the number of shirts is 5
Step 3
finally, replace the value of x = 5, to know the cost
[tex]\begin{gathered} Cost_1=25+5x \\ Cost_1=25+5\cdot5 \\ Cost_1=25+25 \\ Cost_1=Cost_2=50 \end{gathered}[/tex]Step 4
graph
green line-equation (1)
red line= equation (2)
I hope this helps you