Question

If it 8 inch candle burns at 7/10 inch per hour and a 6 inch candle Burns at 1/5 inch per hour after how many hours would both candles be the same height

Answer 1

We must solve

$8 - \frac{7}{10}x = 6 - \frac{1}{5}x \\ or \\ 80 - 7x = 60 - 2x \\ now \\ 20 = 5x \: so \: x = 4$
Means the candles will be the same size in 4 hours