Question 258105
Based on the information we get the following inequality:
(i) {{{18T + 15R <= 450}}}
where T = spare tires and R = repair kits
Solving for T, we get
(ii) {{{T <= (450-15R)/18}}} 
we need to create a list of possible tire - repair kit combinations.
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In terms of T,R we have
6,20 and 12,15
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15 tires and 10 repair kits will cost $420 which is in their budget.