<p>Hi if you please solve these questions:
1)In the XY plane , point P is the reflection of the point with coordinate (3,1) across the line Y=X .
point T is the reflection of point P across the Yaxis. What is the coordinate of T ?
The answer is (-1,3) how and why?
2) a cube is made from 27 small cubes , each with edge of lengh 1.if one cube is renoved , what what willbe the surface area of the remaining solid?
3) the bar graph above shows the number of students who were absent from Jackson high school each day last week
MONDAY:25
TUESDAY. :20
WEDNESDAY:10
THURSDAY:15
FRIDAY:20
of those students, 8 were absent exactly 2 days each ,1 was absent 3 days , and no students were absent more than 3 days. If 5 persent of students in the school were absent at least 1 day last weak , how many students are enrolled in Jackson high school? The answer is1600 , how and why? :-B </p>
<ol>
<li><p>P is located at (1,3). Reflect P across the y-axis to get T=(-1,3).</p></li>
<li><p>Not enough info. Originally the cube has a surface area of 69 = 54 sq units. If a vertex cube is removed, the surface area is still 54 sq units. If a cube on the center of a face is removed, for example, the new surface area is 58 sq units.</p></li>
<li><p>25+20+10+15+20 = 90 total absences. If x is the # of students absent exactly one day, then x<em>1 + 8</em>2 + 13 = 90 --> x = 71, and 71+8+1 = 80. 80 is 5% of the school’s population, so there are 1600 students.</p></li>
</ol>
<p>Thank you very much for your help , but l still have two questions:
1)how does P located at (1,3)?
2) why the cube on the center affects the area:what is the rule? 
</p>
<ol>
<li><p>You’re reflecting across the line y=x, so the coordinates swap ((3,1) goes to (1,3)). Can be proven rigorously, but best is to draw it out and visualize the reflection.</p></li>
<li><p>The cube on the center of a face has 1 face exposed. If you remove it, five faces are exposed. Each face has a surface area of 1 sq unit so the surface area increases by 4. But if you remove a vertex cube, the surface area is unchanged. Since I don’t know which cube is removed, there is not enough info. The rule: visualize it.</p></li>
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<p>Thant you , Iam gratful for your assistance 
</p>