If you were to use the substitution method to solve the following system, choose the new equation after the expression equivalent to x from the second equation is substituted into the first equation.
3x + 2y = −21
x − 3y = 4
a. 3(3y + 4) + 2y = −21
b. 3(−3y + 4) + 2y = −21
c. 3x + 2(3y + 4) = −21
d. 3x + 2(−3y + 4) = −21

Option A

Step-by-step explanation:

Step 1: Naming both equations:

Step 2: Isolating x in Eq. 2

Step 3: Replacing x in Eq. 1

Therefore, the answer is Option A

hello,

b) 62.47% of the students are between 14 and 18 years old.

step-by-step explanation:

mean = 15 and standard deviation = 2

student between 14 to 18

formula used z-score

for age 14 , z score

using z-table , p(z> -0.5)=0.3085

for age 18 , z score

using z-table , p(z< 1.5)=0.9332

p(-0.5< z< 1.5)=0.9332-0.3085 = 0.6247

thus, 62.47% of the students are between 14 and 18 years old.

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step-by-step explanation: