Let,
digital cameras be "x"
video cameras be "y"
Now,
According to the question,
5x + 3y = $3,213..................................................equation (1)
y = 4x..................................................................equation (2)
Taking equation (1)
5x + 3y = $3,213
Substituting the value of "y" from equation (2), we get,
5x + 3(4x) = $3,213
5x + 12x = $3,213
17x = $3,213
x = $3,213 / 17
x = $189
Taking equation (2)
y = 4x
Substituting the value of "x", we get,
y = 4 ($189)
y = $756
Now,
John buys a digital and a video camera. So, it costs him ($189 + $756) = $945
