1. **Problem statement:** Add and subtract the following decimal numbers: a) $49.84 + 18.6$ b) $75.8 + 23.49$ c) $50.03 - 6.72 - 15.55$ 2. **Formula and rules:** - When adding or subtracting decimals, align the decimal points. - Add or subtract digits column-wise starting from the right. - Carry over if sum exceeds 9 in addition. - Borrow if needed in subtraction. 3. **Step-by-step solutions:** **a) $49.84 + 18.6$** Align decimals: $$\begin{array}{r r r r} 4 & 9 & . & 8 4 \\ + & 1 & 8 & . 6 0 \\ \hline \end{array}$$ Add from right: $4 + 0 = 4$ $8 + 6 = 14$, write 4 carry 1 $9 + 8 + 1 = 18$, write 8 carry 1 $4 + 1 = 5$ Result: $$49.84 + 18.6 = 68.44$$ **b) $75.8 + 23.49$** Align decimals: $$\begin{array}{r r r r} 7 & 5 & . & 8 0 \\ + & 2 & 3 & . 4 9 \\ \hline \end{array}$$ Add from right: $0 + 9 = 9$ $8 + 4 = 12$, write 2 carry 1 $5 + 3 + 1 = 9$ $7 + 2 = 9$ Result: $$75.8 + 23.49 = 99.29$$ **c) $50.03 - 6.72 - 15.55$** First subtract $6.72$ from $50.03$: $$\begin{array}{r r r r} 5 & 0 & . & 0 3 \\ - & 6 & . & 7 2 \\ \hline \end{array}$$ Subtract from right: $3 - 2 = 1$ $0 - 7$ not possible, borrow 1 from 0 in tens place: Intermediate step: $$\cancel{0} \to \cancel{10}$$ $10 - 7 = 3$ $9 - 6 = 3$ (after borrowing) $4 - 0 = 4$ Result: $$50.03 - 6.72 = 43.31$$ Now subtract $15.55$: $$\begin{array}{r r r r} 4 & 3 & . & 3 1 \\ - & 1 & 5 & . 5 5 \\ \hline \end{array}$$ Subtract from right: $1 - 5$ not possible, borrow 1 from 3: $$\cancel{3} \to \cancel{2}$$ $11 - 5 = 6$ $2 - 5$ not possible, borrow 1 from 3 in tens place: $$\cancel{3} \to \cancel{2}$$ $12 - 5 = 7$ $2 - 5$ not possible, borrow 1 from 4: $$\cancel{4} \to \cancel{3}$$ $12 - 5 = 7$ $3 - 1 = 2$ Result: $$43.31 - 15.55 = 27.76$$ 4. **Final answers:** a) $68.44$ b) $99.29$ c) $27.76$