Answer:
<h3><u>(54x+10)</u> is the right answer.</h3>
You said that M is 13.7% of N
In algebraic notation M = 0.137 N
Divide each side by 0.137 : N = M / 0.137 = 7.3 M (rounded)
Online or in a real book, you can look up the radius of Mars.
Then write it in place of 'M' in this solution, and you'll have
an actual number for the radius of Neptune.
Let <em>n</em> be the unknown number. We can write it as
<em>n</em> = 10<em>a</em> + <em>b</em>
with <em>a</em> and <em>b</em> integers between 1 and 9 (either with positive or negative sign).
Reversing the digits gives another number
<em>m</em> = 10<em>b</em> + <em>a</em>
The first number is increased by 54 when the digits are reversed, which means
<em>m</em> = <em>n</em> + 54 → 10<em>b</em> + <em>a</em> = 10<em>a</em> + <em>b</em> + 54 → 9<em>b</em> - 9<em>a</em> = 54 → <em>b</em> - <em>a</em> = 6
The digit in the tens place of <em>n</em> is 3 times the digit in the ones place, so
<em>a</em> = 3<em>b</em>
Substitute this into the previous equation and solve for <em>b</em> :
<em>b</em> - <em>a</em> = <em>b</em> - 3<em>b</em> = -2<em>b</em> = 6 → <em>b</em> = -3
Solve for <em>a</em> :
<em>a</em> = 3<em>b</em> = 3(-3) = -9
Then the original number is <em>n</em> = 10<em>a</em> + <em>b</em> = 10(-9) + (-3) = -93
