Alotion is made from an oil blend costing $1.50 per ounce and glycerin costing $1.00 per ounce. four ounces of lotion costs $5.50.

X - ounces of an oil blend,
y - ounces of glycerin;
1.5 · x + 1 · y = 5.50
x + y = 4

1.5 x + y =  5.5
     x  + y =  4      / · ( -1 )

1.5 x + y = 5.5
+
   - x  - y  = - 4

   0.5 x  =  1.5
   x = 1.5  : 0.5
   x = 3
   3  +  y  = 4
   y = 1
   There are 3 ounces of an oil blend and 1 ounce of glycerin in 4 ounces of lotion.