Mathematics for IGCSE & O level - Equations (Section 6 - No. 9)
When would you use substitution to solve a system of equations?
When one equation is already solved for a variable.
When both equations are linear.
When the coefficients of the variables are easy to manipulate.
When the coefficients of the variables are fractions.
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Substitution is best when one equation is pre-solved for a variable.