Question 445895
price of audio cassette, a
price of video cassette, v


{{{system(7a+3v=1110,5a+4v=1350)}}}


Multiplying each to get coefficient 12 for v,
{{{system(28a+12v=4440,15a+12v=4050)}}}
Subtract second from first
{{{13a=390}}}
{{{highlight(a=30)}}}


Substitute a found into first equation
{{{7*30+3v=1110}}}
{{{3v=1110-210}}}
{{{v=370-70}}}
{{{highlight(v=300)}}}