The rule for negative exponents is that if the exponent is negative to begin with, in order to make it negative, you put it into the denominator of a fraction, and raise it to whatever the power is. To go from positive exponents (those that are already in the denominator), move it up to the numerator and make the exponent negative. So your solution would be 5x^-2
The initial expression is:

So we can solve for r so:
When angles and sides are all equal
Answer:
62.7
Step-by-step explanation:
165 * 0.38 = 62.7
This is assuming you mean an object weights 38% less on mars then earth, if its the other way around(they weight 38% more on mars then earth) it would be,
165 * 1.38 = 227.7
Yes because 3*5 = 15
Factors multiply to get the product.