Sam had 80 foreign stamps and local stamps. After giving away 1/3 of his foreign stamps and 10 local stamps, he had an equal number of foreign stamps and local stamps left. How many local stamps did he have in the beginning?
We start by defining variables:
x is the number of foreign stamps, y is the number of local stamps.
From the problem we derive the 2 equations:
x+y=80
(2/3)x=y-10
Solving by substitution we get
(2/3)x+10=y
x+(2/3)x+10=80
(5/3)x+10=80
(5/3)x+10-10=80-10
(5/3)x=70
x=70/(5/3)
x=70*(3/5)
x=42
We can now back substitute into the original equation:
42+y=80
42-42+y=80-42
We arrive at y=38.
Sam started with 38 local stamps.
We start by defining variables:
x is the number of foreign stamps, y is the number of local stamps.
From the problem we derive the 2 equations:
x+y=80
(2/3)x=y-10
Solving by substitution we get
(2/3)x+10=y
x+(2/3)x+10=80
(5/3)x+10=80
(5/3)x+10-10=80-10
(5/3)x=70
x=70/(5/3)
x=70*(3/5)
x=42
We can now back substitute into the original equation:
42+y=80
42-42+y=80-42
We arrive at y=38.
Sam started with 38 local stamps.
