1. **State the problem:** Albert had 16.10 less than Peter. After Peter gave 2.50 to Albert, Peter had 4 times as much money as Albert. 2. **Define variables:** Let $P$ be the amount of money Peter had at first. Let $A$ be the amount of money Albert had at first. 3. **Write equations from the problem:** From the first statement: $$A = P - 16.10$$ After Peter gives 2.50 to Albert: Peter's money: $P - 2.50$ Albert's money: $A + 2.50$ From the second statement: $$P - 2.50 = 4(A + 2.50)$$ 4. **Substitute $A$ from the first equation into the second:** $$P - 2.50 = 4((P - 16.10) + 2.50)$$ 5. **Simplify inside the parentheses:** $$(P - 16.10) + 2.50 = P - 13.60$$ So: $$P - 2.50 = 4(P - 13.60)$$ 6. **Expand the right side:** $$P - 2.50 = 4P - 54.40$$ 7. **Bring all terms to one side:** $$P - 2.50 - 4P + 54.40 = 0$$ Simplify: $$-3P + 51.90 = 0$$ 8. **Isolate $P$:** $$-3P = -51.90$$ $$P = \frac{-51.90}{-3}$$ 9. **Simplify the fraction:** $$P = \cancel{\frac{-51.90}{-3}} = 17.30$$ 10. **Final answer:** Peter had 17.30 at first.