x+y=16
xy=12
x+y=16
subtract x from both side
y=16-x
subsitute for y
x(16-x)=12
16x-x^2=12
subtract add x^2 to both sides
16x=12+x^2
subtract 16x from both sides
x^2-16x+12=0
try and factor
can't
use quadratic equation which is
x=

when you have
ax^2+bx+c=0
x^2-16x+12=0
a=1
b=-16
c=12
subsitute
x=

x=

x=

x=

x=

x=

or

the answer is
the numbers are

and

or
aprox 0.788897 and 15.2111