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5a-b=12 call this Equation (1)
\n" ); document.write( "7a-3b=20 call this Equation (2)
\n" ); document.write( "to solve this we rearrange one of the equations, let's do equation (1).
\n" ); document.write( "Rearranging (1) gives
\n" ); document.write( "-b=12-5a Let's change the signs of each term (this is the same as multiplying everything by -1) giving
\n" ); document.write( "b=5a-12 let's call this equation (3)
\n" ); document.write( "Substitute this value into equation (2) giving
\n" ); document.write( "7a-3*(5a-12)=20 multiplying out the bracket gives
\n" ); document.write( "7a-15a+36=20
\n" ); document.write( "simplifying this gives
\n" ); document.write( "-8a=-16
\n" ); document.write( "thus
\n" ); document.write( "a=2
\n" ); document.write( "Now we have a value for a we can use this to work out b
\n" ); document.write( "substitute a=2 into one of the equations (1), (2) or (3)
\n" ); document.write( "(3) seems the simplest one so we'll use that.
\n" ); document.write( "b=5*2-12
\n" ); document.write( "therefore
\n" ); document.write( "b=-2
\n" ); document.write( " \n" ); document.write( "