The garden has four quarters. three quarters are planted with basil. one quarter is planted with sage. The strips represent quarters. So that means that three strips represent three quarters. Well one strip represents one quarter.
Cd is equal to this: first calculate AB by sin30 which is radical 3 then by sin45 you know bc is radical 3 too then by fisaghures ( idk what you call it)
calculate bd at the end you just gotta do this: bd-bc
0.45 i think just into fractions