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1.
31.29/6 = 5.215
5.215 × 2 = 10.43
2 brushes cost $10.43
2.
31.29 × 3 = 93.87
93.87 * 10% = 9.387
93.87 - 9.387 = 84.483
3 cases would cost $84.48
His brother would be 7 years old.
4*2^-4+5
4*<span>0.0625+5
0.25+5
final answer will be 0.30</span>
Since the number ranges between 3 and 10, an equation can't be made because the number is always unknown or can be different every time
-8400/68 simplifies to to -2100/17, dolphins/year, so 2100 less dolphins every 17 years.
and we can just divide those to get the decimal amount of -123.53, which means, 123.53 less dolphins every year.
of course, there's no such a thing as 0.53 of a dolphin, so, we can say "about" 123 less dolphins per year.