In order to find the value of ∠EFB here, we have to note our angle relationships.
We know that ∠CFE is already 90°. We also know that ∠CFA is 90°. Angle ∠AFB is inside ∠CFA. Since we know the measure of ∠AFB, we can find the measure of ∠BFC.
Now that we know ∠CFE and ∠BFC, which together make ∠BFE, we can add these angles up.