- A−2
- B5
- C−3
- D3
Step-by-Step Solution
From the first equation . Substituting: → → , so . Check: ✓ and ✓. Answering −2 reports instead of ; −3 comes from dropping the sign when back-substituting.
Answer: D) 3
Solve by substitution: and . Find .
Class 10Pair of Linear Equations in Two VariablesAlgebra — Systems of Equations
Key idea: Substitution method
**Steps**:
1. From one equation, express ONE variable in terms of the other.
2. Substitute into the OTHER equation. You get a one-variable equation.
3. Solve.
4. Plug back to find the other variable.
**Example**: ... (i); ... (ii).
- From (ii): .
- Substitute in (i): → → .
- Then .
- Solution: .
1. From one equation, express ONE variable in terms of the other.
2. Substitute into the OTHER equation. You get a one-variable equation.
3. Solve.
4. Plug back to find the other variable.
**Example**: ... (i); ... (ii).
- From (ii): .
- Substitute in (i): → → .
- Then .
- Solution: .
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