Question 255856
Call smaller side x, then larger side is x + 25
small side + border is x + 10 ( border on each side)
large side is x + 35
Area of border is (x + 10)(x + 35) -(x)(x+25) = 1350
Expanding ( x^2 + 45x + 350 ) - (x^2 + 25x) = 1350
20x + 350 = 1350
x = 1000/20 = 50 cm

Check: Picture is 50 x 75 = 3750 cm sq
with border is 60 x 85 = 8100 cm sq
Difference is 1350 cm sq