Hello can someone me with 3 to find the area of the triangle and number 5 to find the missing dimension and explain it thx

In #3, you are given the base and the height of the triangle, so you need only substitute these numerical values into the formula for the area of a triangle of base b and height h:
       
       bh
A=    Would you please do this now?  A = ?
         2

2936688fdyvdyfhhtdhjwkkviyuw