Chloe and denise bought a identical t-shirts from the same shop. chloe bought on monday when there was a 15% off the original price. denise bought on froday when there was 20% off the original price. chloe paid 35p more than denise. what was the original price?

The original price was 7.

Chloe got a 15% discount; this means she paid 100-15 = 85% of the price.  Letting x be the price, Chloe paid 0.85x.

Denise got a 20% discount; this means she paid 100-20 = 80% of the price.  Denise paid 0.8x.

We know that Chloe paid 35p more; this gives us the equation
0.85x = 0.8x + 0.35

We do not want a variable on both sides, so we subtract 0.8x from both:
0.85x - 0.8x = 0.8x + 0.35 - 0.8x
0.05x = 0.35

Divide both sides by 0.05:
0.05x/0.05 = 0.35/0.05
x = 7