1. Problem: Find the value of $x$ if $2x + 3 = 11$. Formula: Use the equation $2x + 3 = 11$ and solve for $x$. Step 1: Subtract 3 from both sides: $2x = 11 - 3$ Step 2: Simplify: $2x = 8$ Step 3: Divide both sides by 2: $x = \frac{8}{2} = 4$ Answer: $x = 4$ 2. Problem: Calculate the sum of the first 5 natural numbers. Formula: Sum of first $n$ natural numbers is $\frac{n(n+1)}{2}$. Step 1: Substitute $n=5$: $\frac{5(5+1)}{2}$ Step 2: Simplify: $\frac{5 \times 6}{2} = \frac{30}{2} = 15$ Answer: $15$ 3. Problem: Find the area of a rectangle with length 7 units and width 3 units. Formula: Area $= \text{length} \times \text{width}$. Step 1: Multiply length and width: $7 \times 3 = 21$ Answer: Area $= 21$ square units 4. Problem: Simplify the expression $5(2x - 3) + 4x$. Step 1: Distribute 5: $5 \times 2x - 5 \times 3 + 4x = 10x - 15 + 4x$ Step 2: Combine like terms: $10x + 4x - 15 = 14x - 15$ Answer: $14x - 15$ 5. Problem: Find the value of $y$ if $3y - 7 = 2y + 5$. Step 1: Subtract $2y$ from both sides: $3y - 2y - 7 = 5$ Step 2: Simplify: $y - 7 = 5$ Step 3: Add 7 to both sides: $y = 5 + 7 = 12$ Answer: $y = 12$