Let [tex] x [/tex] be the most the manager can pay the suppliers.
Then, we know from the information given in the question that the manager needs a 30% markup based on cost.
Therefore, the guiding equation will be:
[tex] x+\frac{30}{100}x\leq 10 [/tex]
because $10 is the most people will pay for a neck warmer.
Thus, the above equation will become:
[tex] x+0.3x\leq 10 [/tex]
[tex] 1.3x\leq 10 [/tex]
[tex] x\leq \frac{10}{1.3}=7.69 [/tex]
[tex] \therefore x\leq 7.69 [/tex]
Thus, the most a manager can pay the suppliers for neck warmers and still keep the selling price at $10 is $7.69