Move the decimal so there is one non-zero digit to the left of the decimal point. The number of decimal places you move will be the exponent on the
10. If the decimal is being moved to the right, the exponent will be negative. If the decimal is being moved to the left, the exponent will be positive.
You have to use a system. the first would be x + y = 12 since she has 12 coins. the other equation would be 0.05x + 0.1y = 0.95 (an easier way is 5x + 10y = 95 if you clear it). now you just solve using substitution or elimination.
