The earth is 93 million miles away from the sun. 93 million times 10 is 930,000,000 away. Mars is currently 141.6 million miles from the sun. Assuming the planets were in a straight line you would subtract from 141.6 million miles the 93 million miles so that would put us within 48,600,000 miles of Mars. So the answer is we would be closest to Mars.
Questions like this ("how much higher is x than y?") are answered by computing the ratio of the two quantities.
In fact, for example, the answer to "how much higher is 10 than 5?" is 2, because 10:5 = 2, and indeed 10 is twice as much as 5.
So, we have

So, the melting temperature of platinum is about one time and a half higher than the melting temperature of gold.