Let's let x be the number of t-shirts.
So the first company charges $43 plus $9 per shirt. For x shirts, the cost is the base fee plus 9 times x, or

.
The second company charges a $58 fee plus $8 per shift. The cost is
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.
Now, we want to find which fee is less when we are buying 20 shirts. We plug in 20 for x.
The first company charges
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.
The second company charges

.
The costs are VERY close, but the second company ultimately charges
less.