Uh u fine with algebra? Cuz I’m not used to using model and I suck at it so

Let y be the breadth

y x 7/2 = 7y/2 (length of rectangle)

7y/2 x y = 126 (area of rectangle formula: L x B)

7y^2/2 = 126 (simplified by multiplying the y as a fraction. ^2 means squared which is power 2. This is when u multiply the same term twice)

7y^2 = 252 (multiplied both sides by 2 to get rid of denominator)

y^2 = 36 (simplified to get coefficient of 1 so we can square root it)

y = ± √36 (± means plus minus as square roots can have 2 ans as shown below)

y = -6(rej) and 6 (2 ans cuz (-6) x (-6) = 36 & 6 x 6 is also 36. You’ll learn this in sec 1 & 2 so if u don’t understand it’s fine. Just make sure u understand how I got the ans)

7/2 x 6 = 21 (Length)

Explanation: so I rejected the -6 and cuz length and breadth cannot be negative as it wouldn’t make sense.