1.) Let c be Mr. Charbonneau's current age and s be Mr. Seward's current age. The sum of their ages is 96, so c + s = 96. In 10 years, Mr. Charbonneau will be c + 10 years old. At this time, he will be 14 years older than Mr. Seward is now, which is s years old, so c + 10 = s + 14. Solve the system of equations by elimination.
c + 10 = s + 14 (subtract s from both sides and 10 from both sides)
c - s = 4
Add this equation and the first equation c + s = 96 together to solve for c.
(c + s = 96) + (c - s = 4)
2c = 100
c = 50
Now go back to any equation to solve for s.
c + s = 96
50 + s = 96
s = 46
Mr. Charbonneau is 50 years old and Mr. Seward is 46 years old.
2.) Let x be the smaller number and y be the larger number. One number, which would be the smaller, is 7 less than the other, so x = y - 7. Also, six times the smaller number is 8 more than the larger number, so 6x = y + 8. Solve the system by substitution.
6x = y + 8 (substitute y - 7 for x)
6(y - 7) = y + 8
6y - 42 = y + 8
5y - 42 = 8
5y = 50
y = 10
x = y - 7
x = 10 - 7
x = 3
The numbers are 3 and 10.
3.) Slope-intercept form is y = mx + b, where m is the slope and b is the y-intercept. Perpendicular lines have slopes that are opposite reciprocals (have a product of -1). Line y = 2x + 3 has a slope of 2, so a line perpendicular to it has a slope of -1/2, thus its equation so far in slope-intercept form is y = (-1/2)x + b. This line also has the same x-intercept as x + 3y + 10 = 0. Solve for the x-intercept, which is when y = 0.
x + 3y + 10 = 0
x + 3(0) + 10 = 0
x + 10 = 0
x = -10
The x-intercept is point (-10, 0). Substitute this point into the equation y = (-1/2)x + b for x and y respectively to solve for b.
y = (-1/2)x + b
0 = (-1/2)(-10) + b
0 = 5 + b
-5 = b
The equation of the line is y = (-1/2)x - 5.