1. When an architect builds a building, they need to make sure that the foundation is strong enough to support the building's weight.2. The solid floor is resistant to scratches.3. The firm fabric of the shirt makes it resistant to tears and rips.
 strong solid firmstrong 是堅固或紮實最貼切又最簡單的說法，solid 是硬的意思，firm 有硬跟紮實的意思
I have been wecking my brain on this tough math question but I still cannot solve it.