An internet service provider charges $18 per month plus initial set up fee. once customer paid a total of $81 after 2 months of service. what is the initial set up fee and how much does it cost after 5 months of service

18*m +fee = charge

at 2 months  the charge is 81  so substitute in

18*2 +fee = 81

36+fee=81

subtract 36 from both sides

fee = 45

for 5 months what is the charge

18*m +fee = charge

18*5 +45 = charge

90 + 45 = charge

135

the initial fee is $45 and the 5 month fee is $135

< xcy ≅ < xby

step-by-step explanation:

in δcax and δbax,

so, δcax ≅ δbax (side-angle-side or sas)

since δcax ≅ δbax, we can conclude < acx ≅ < abx

in δacy and δaby,

so, δacy ≅ δaby (side-angle-side or sas)

since δacy ≅ δaby, we can conclude < acy ≅ < aby

now,

< acy ≅ < aby

=> < acx + < xcy ≅ < abx + < xby

=> < acx + < xcy ≅ < acx + < xby   (since < acx ≅ < abx already proved above)

subtracting < acx from both sides, we get

< acx + < xcy -< acx ≅ < acx + < xby -< acx

cancelling out < acx and -< acx from both sides, we get

< xcy ≅ < xby (proved)