Which two numbers should be interchanged to make the given equation correct?
(NOTE: Numbers must be interchanged and not the constituent digits. E.g., if 2 and 3 are to be interchanged in the equation 43 × 3 + 4 ÷ 2, then the interchanged equation is 43 × 2 + 4 ÷ 3.)
79 – 43 + (23 + 75) × 3 – (30 ÷ 15) × 4 = 175

Correct option is C

Given:
79 – 43 + (23 + 75) × 3 – (30 ÷ 15) × 4 = 175
Concept: To solve this, we need to interchange the numbers as directed in the options in the given equation to solve the equation. For this, we follow the BODMAS rule (Brackets, Orders (i.e., powers, and square roots, etc.), Division, Multiplication, Addition, and Subtraction).
Explanation:
Option (a): 3 and 4
79 – 43 + (23 + 75) × 4 – (30 ÷ 15) × 3 = 175
79 – 43 + 98 × 4 – 2 × 3 = 175
79 – 43 + 392 – 6 = 175
471 – 43 – 6 = 175
422 ≠ 175 (This option does not satisfy the equation)
Option (b): 75 and 79
75 – 43 + (23 + 79) × 3 – (30 ÷ 15) × 4 = 175
75 – 43 + 102 × 3 – 2 × 4 = 175
75 – 43 + 306 – 8 = 175
381 – 43 – 8 = 175
330 ≠ 175 (This option does not satisfy the equation)
Option (c): 75 and 30
79 – 43 + (23 + 30) × 3 – (75 ÷ 15) × 4 = 175
79 – 43 + 53 × 3 – 5 × 4 = 175
79 – 43 + 159 – 20 = 175
238 – 43 – 20 = 175
175 = 175 (This option satisfies the equation)
Option (d): 23 and 43
79 – 23 + (43 + 75) × 3 – (30 ÷ 15) × 4 = 175
79 – 23 + 118 × 3 – 2 × 4 = 175
79 – 23 + 354 – 8 = 175
433 – 23 – 8 = 15
402 ≠ 175 (This option does not satisfy the equation)
The final answer is option (c).