The perimeter of a rectangle is given by

perimeter = 2(length + width)

You want

perimeter > 80 cm

We can substitute the known quantities and relations ...

2(length + 26 cm) > 80 cm

length + 26 cm > 40 cm (divide both sides by 2)

length > 14 cm (subtract 26 cm from both sides)

perimeter = 2(length + width)

You want

perimeter > 80 cm

We can substitute the known quantities and relations ...

2(length + 26 cm) > 80 cm

length + 26 cm > 40 cm (divide both sides by 2)

length > 14 cm (subtract 26 cm from both sides)