Distribute 7sqrt(6) to the first term, 2sqrt(10)

We look for the largest perfect square factor of 60. $60 = 4 \times 15$.

$$14\sqrt{60} = 14\sqrt{4 \times 15} = 14 \times \sqrt{4} \times \sqrt{15} = 14 \times 2 \times \sqrt{15} = 28\sqrt{15}$$

We look for the largest perfect square factor of 12. $12 = 4 \times 3$.

$$-35\sqrt{12} = -35\sqrt{4 \times 3} = -35 \times \sqrt{4} \times \sqrt{3} = -35 \times 2 \times \sqrt{3} = -70\sqrt{3}$$

The simplified expression is the sum of the results from Step 2 and Step 4:

$$28\sqrt{15} - 70\sqrt{3}$$

Since $\sqrt{15}$ and $\sqrt{3}$ are not like terms, they cannot be combined further.