How do you solve for r in #ax + r = 7#?

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Answer 1 · 2016-06-01T20:38:56

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Given:#" "ax+r=7#
#color(green)("Using shortcut - based on consequence of first principles")#

Move #+ax# to the other side of the = but change the sign to minus

#color(brown)(+ax+r=7) color(blue)(" "->" "r=7-ax)#

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#color(green)("Using first principles")#

Subtract #color(blue)(ax)# from #underline("both sides.")#

#color(brown)(ax + r color(blue)(-ax)=7color(blue)(-ax))color(magenta)(" "larr" balanced equation")#

But #ax-ax=0#

#0+r=7-ax#

#r=7-ax#