How much Lea saves after one month: 700 x 4 = 2800 

3/7 of her savings spent: 3/7 x 2800 = 1200

Discount on bike: 1200 – 180 = 1020 

Fraction of new bike after discount (denominator should be the original price): 1020/1200

Simplest form: 17/20 

Personally, I think $1200 was the price AFTER discount, so the original price was $1380.

Reason being, if the sale price were $1020, then it would not be right to say that she spent 3/7 of  her savings on the bicycle.