102 of runner's races were 10-kilometer races.
Step-by-step explanation:
Given,
Total kilometers finished = 1500 km
Number of 15 km races = 32
Number of 10 km races = x
Therefore;
15*32+10x=1500
[tex]480+10x=1500\\10x=1500-480\\10x=1020[/tex]
Dividing both sides by 10
[tex]\frac{10x}{10}=\frac{1020}{10}\\x=102[/tex]
102 of runner's races were 10-kilometer races.
Keywords: variable, division
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