To subtract these radicals together their radicands must be the same:

7\( \sqrt{28} \) - 9\( \sqrt{7} \)
7\( \sqrt{4 \times 7} \) - 9\( \sqrt{7} \)
7\( \sqrt{2^2 \times 7} \) - 9\( \sqrt{7} \)
(7)(2)\( \sqrt{7} \) - 9\( \sqrt{7} \)
14\( \sqrt{7} \) - 9\( \sqrt{7} \)

Now that the radicands are identical, you can subtract them:

A ratio of 3:1 means that there are 3 home fans for every one visiting fan. So, of every 4 fans, 3 are home fans and \( \frac{3}{4} \) of every fan in the stadium is a home fan:

35,000 fans x \( \frac{3}{4} \) = \( \frac{105000}{4} \) = 26,250 fans.

The first few multiples of 3 are [3, 6, 9, 12, 15, 18, 21, 24, 27, 30] and the first few multiples of 9 are [9, 18, 27, 36, 45, 54, 63, 72, 81, 90]. The first few multiples they share are [9, 18, 27, 36, 45] making 9 the smallest multiple 3 and 9 have in common.

To subtract these fractions, first find the lowest common multiple of their denominators. The first few multiples of 8 are [8, 16, 24, 32, 40, 48, 56, 64, 72, 80] and the first few multiples of 12 are [12, 24, 36, 48, 60, 72, 84, 96]. The first few multiples they share are [24, 48, 72, 96] making 24 the smallest multiple 8 and 12 share.

Next, convert the fractions so each denominator equals the lowest common multiple:

\( \frac{8 x 3}{8 x 3} \) - \( \frac{6 x 2}{12 x 2} \)

\( \frac{24}{24} \) - \( \frac{12}{24} \)

Now, because the fractions share a common denominator, you can subtract them:

\( \frac{24 - 12}{24} \) = \( \frac{12}{24} \) = \(\frac{1}{2}\)

If the tiger has consumed 42 pounds of food in 6 days that's \( \frac{42}{6} \) = 7 pounds of food per day. The tiger needs to consume 91 - 42 = 49 more pounds of food to reach 91 pounds total. At 7 pounds of food per day that's \( \frac{49}{7} \) = 7 more days.