Answer:
74
Step-by-step explanation:
You just have to substitute r with 5.
Now, the equation looks like this:
[tex]15(5)-1[/tex]
Next, solve [tex]15*5[/tex] first according to PEMDAS
And [tex]15*5[/tex] equals 75
[tex]\frac{\left[\begin{array}{ccc}1&5\\5\\\end{array}\right] }{75}[/tex]
Lastly, do [tex]75-1[/tex] which equals 74
[tex]\frac{\left[\begin{array}{ccc}7&5\\-1\\\end{array}\right] }{74}[/tex]
Therefore, 74 is your answer.
