A carpenter needs to cut a diagonal brace to support a rectangular frame that measures 85 cm wide by 160 cm long. What angle would be formed

Let's use the tangent to start off, here...so we have

tan Θ = opp / adj  =  160/ 85

So, using the tangent inverse to find Θ, we have

tan^-1 (160 / 85) = about 62.02°

Here's a 1/10 scale pic........