T = how tall
W = how wide.
T = W + 25 is the first equation
5
×
{
2
(
T
+
10
)
}
+
5
×
(
2
×
W
)
=
1350
This equation is the total height adding 5 for the top border and 5 for the bottom border. Then multiplying the total height by the width of the border 5, time 2 because there are two sides that are tall Then adding 5 times two widths.
Now substitute the value of W + 25 for T this gives
# 5 xx (2 xx W + 25 +10)+ 5 xx 2W = 1350 solving for W
5
×
(
2
W
+
50
+
20
)
+
10
W
=
1350
10
W
+
5
(
70
)
+
10
W
=
1350
20
W
+
350
=
1350
20
W
+
350
−
350
=
1350
−
350
20
W
=
1000
W = 50
T = 50 + 25
T = 75