Answer:
Step-by-step explanation:
(a) You use the fact that the lengths RS and ST total the length RT.
RS +ST = RT
(6y+3) +(3y+5) = 80 . . . . . substitute the given values
9y +8 = 80 . . . . . . . . . . . . .simplify
9y = 72 . . . . . . . . . . . . . . . .subtract 8
72/9 = y = 8 . . . . . . . . . . . .divide by the coefficient of y
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(b) Now, the value of y can be substituted into the expressions for RS and ST to find their lengths.
RS = 6y +3 = 6·8 +3
RS = 51
ST = 3y +5 = 3·8 +5
ST = 29
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Check
RS +ST = 51 +29 = 80 = RT . . . . the numbers check OK
