Answer:
x = 8°
Explanation:
from the figure it is understood that the two angles 51 and 4x+7 form an angle of 90°, we can solve with a proportion
51 + 4x + 7 = 90
4x = 90 - 51 - 7
4x = 32
x = 32 : 4
x = 8
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check
51 + 4 x 8 + 7 = 90
90 = 90
same value the answer is good