Answer:
7
Step-by-step explanation:
Substitute x = -4 :
f(-4) = 3 - (-4)
= 3 + 4
= 7
Let Daniel's age be 'x' years , hence, Lisa's age is (x - 5) years. Let Grandma's age be 'y' = 54 years.
Hence,
x(x - 5) = 2/3 × y
x² - 5x = 2 × 54 years / 3
x² - 5x = 36 years
x² - 5x - 36 = 0
∆ = (-5)² - 4(1)(-36) = 25 + 144 = 169
√∆ = √169 = 13

x1 = (5+13)/2, x2 = (5-13)/2
x1 = 9, x2 = -4
Since, age can't be negative,
Daniel's age = x = 9 years.
X = 4y
3x - y = 70
substitute the x in the second equation with the other half of the first equation.
3(4y) - y = 70
12y - y = 70
11y = 70
y = 6.36 repeating, or 6 4/11
now use this to solve first equation
x = 4 (6 4/11)
x = 25.45 repeating
done