An equation is formed of two equal expressions. The number of questions that Lesley answered correctly is 20.
An equation is formed when two equal expressions are equated together with the help of an equal sign '='.
Let the number of correct questions answered be x, while the number of questions incorrectly answered be y.
The total number of questions can be written as,
x + y = 25
Solving the equation for y,
y = 25 - x
The total marks can be written as,
3x - 1y = 55
Substitute the value of y,
3x - 25 + x = 55
4x = 80
x = 20
Hence, the number of questions that Lesley answered correctly is 20.
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