The relationship between bacteria and legumes that results in nitrogen is best described as
a. parasitic
b. mutualistic
c. commensalistic
d. none of the above

The correct answer would be b. mutualistic.

Mutualism is a type of biological interaction between two species in which both the organisms get benefited from each other.

Bacteria present in the root nodules of leguminous plants help the plant in absorbing nitrogen from the soil by fixing atmospheric nitrogen into nitrogenous absorbable compounds such as ammonia.

In return, bacteria get shelter and food in the form of carbohydrates from the plant.

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)