Let
x ----> number of boxes of ballpoint pens
y ----> number of boxes of felt-tip pens
we have that
4.37x+3.43y=62.73 -------> equation A
x=4y ----> equation B
solve the system of equations
substitute equation B in equation A
4.37(4y)+3.43y=62.73
solve for y
17.48y+3.43y=62.73
20.91y=62.73
y=3
Find out the value of x
x=4(3)
x=12
therefore
He buys 12 boxes of ballpoint pens and 3 boxes of felt-tip pens