You can either solve the equation for the indicated variable and then determine the value of that variable directly using the given information; or you can plug in the given values directly and solve the resulting equation for the value of the variable.
Either way, this is something you need to do on your own -- we aren't here to do your calculations for you.
Your saying in your note that you are going back to college and having trouble getting up to speed is the kind of thing we ask you to say when you first post your question. The way you posted this question (and several others), it appeared to us as though you were simply wanting us to do all your work for you....
So for this example....
(1) Solve the given algebraic equation for h using algebra, then find the value of h directly....
A = (1/2)h(a+b)
isolate the "h" by getting rid of (moving) the "(1/2)" and the "(a=b)"
A/(a+b) = (1/2)h [divide both sides by (a+b)]
2A/(a+b) = h [multiply both sides by 2]
Now evaluate with the given input:
h = 2A/(a+b) = (2*39)/(4+9) = 78/13 = 6
or (2) plug in the given values and solve the resulting equation....
You can put this solution on YOUR website! Find h if A = 39; a = 4; b = 9
A= 1/2h(a+b)
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Sub what you're given.
39 = h*(4+9)/2
78 = h*13
etc
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PS A= 1/2h(a+b) is ambiguous.
Could be
or
