Combine like terms in the following expression: 4 + 3(1−3m)

the parenthesis part you must distribute it.

4 + 3 x 1 and 3 x -3m

4 + 3 -9m

now you combine like terms which 4 and 3 are the same type of term

4+3 = 7 - 9m is your answer

we have three similar triangles, because each has a right angle and shares an angle.   let's write the angles in order: opposite to short leg, long leg, hypotenuse.

cab similar to bad similar to cbd

or as ratios,

ca: ab: cb = ba: ad: bd = cb: bd: cd

we also know

ac = ad + cd

(ad+cd): ab: cb = ba: ad: bd = cb: bd: cd

(ad+cd)/cb=cb/cd

we have cb=6, ad=5 and seek x=cd.

we reject the negative root and conclude x=4

answer: 4