Question 877564
x is how many 20 cent coins
y is how many 50 cent coins
y=3+x, three more 50 cent coins than 20 cent coins.


The money units sum is {{{20x+50y=290}}}, simplified as {{{2x+5y=29}}}.
Substitute for y.
{{{2x+5(3+x)=29}}}
{{{2x+15+5x=29}}}
{{{7x+15=29}}}
{{{7x=14}}}
{{{highlight(x=2)}}}, {{{highlight(y=5)}}}.