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Solve the following pair of linear equations by the substitution method

(i) 3x – y = 3

9x – 3y = 9

(ii) 0.2x + 0.3y = 1.3

0.4x + 0.5y = 2.3

(i) Given,

\[3x\text{ }-y\text{ }=\text{ }3\text{ }and\text{ }9x\text{ }-3y\text{ }=\text{ }9\]  are the two conditions.

From first condition, we get,

\[x\text{ }=\text{ }\left( 3+y \right)/3\]  

Presently, substitute the worth of x in the given second condition to get,

\[9\left( 3+y \right)/3\text{ }-3y\text{ }=\text{ }9\]  

\[\Rightarrow 9\text{ }+3y\text{ }-\text{ }3y\text{ }=\text{ }9\]  

\[\Rightarrow 9\text{ }=\text{ }9\]  

Hence, y has limitless qualities and since, \[x\text{ }=\text{ }\left( 3+y \right)/3\] , so x additionally has boundless qualities.

(ii) Given,

\[0.2x\text{ }+\text{ }0.3y\text{ }=\text{ }1.3\text{ }and\text{ }0.4x\text{ }+\text{ }0.5y\text{ }=\text{ }2.3\] are the two conditions.

From first condition, we get,

\[x\text{ }=\text{ }\left( 1.3-0.3y \right)/0.2\text{ }\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\left( 1 \right)\]  

Presently, substitute the worth of x in the given second condition to get,

\[0.4\left( 1.3-0.3y \right)/0.2\text{ }+\text{ }0.5y\text{ }=\text{ }2.3\] 

\[\Rightarrow 2(1.3-0.3y)\text{ }+\text{ }0.5y\text{ }=\text{ }2.3\] 

\[\Rightarrow 2.6-0.6y\text{ }+\text{ }0.5y\text{ }=\text{ }2.3\] 

\[\Rightarrow 2.6-0.1\text{ }y\text{ }=\text{ }2.3\] 

\[\Rightarrow 0.1\text{ }y\text{ }=\text{ }0.3\] 

\[\Rightarrow y\text{ }=\text{ }3\]  

Presently, substitute the worth of y in condition (1), we get,

\[x\text{ }=\text{ }\left( 1.3-0.3\left( 3 \right) \right)/0.2\text{ }=\text{ }\left( 1.3-0.9 \right)/0.2\text{ }=\text{ }0.4/0.2\text{ }=\text{ }2\]   Hence, \[x\text{ }=\text{ }2\text{ }and\text{ }y\text{ }=\text{ }3\] .