Maths-
General
Easy
Question
x + 2y = 16
0.5x - y = 10
The solution to the system of equations above is (x, y). What is the value of x ?
- -2
- 2
- 18
- 36
The correct answer is: 18
HINT: Solve the system of equations.
Complete step by step solution:
Let x + 2y = 16…(i) and 0.5x - y = 10…(ii)
Multiply (ii) with 2 to make the coefficients of y to be the same.
On multiplying, we get (ii) to be 2(0.5x - y = 10) = x - 2y = 20
Let x - 2y = 20…(iii)
On adding (i) and (iii),
Then, LHS becomes 2x and RHS will be 16 + 20 = 36
On equating LHS and RHS, we get 2x = 36
On dividing both the sides by 2, we get 
x = 18
Thus the value of x is 18
Hence option C is the correct answer.
Note: We can solve this by multiplying (i) with 0.5. We get (i) to be 0.5x + y = 8 and let this be (iii).By solving (ii)
and (iii), we get the value of y = -1 .By substituting the value of y in (ii) we get the value of x to be 18.
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