Which system of equations has one solution?

A system has one solution when its equations represent lines that intersect at exactly one point. In choice D, adding −2x + 7y = −5 and 2x + 7y = −9 eliminates x and gives 14y = −14, so y = −1; substituting back gives x = 1. The equations therefore determine a single ordered pair, (1, −1).

AI-written and checked against the verified answer.